Evaporation of water by plants. Evaporation of soil moisture What is the danger of disturbing the moisture level?

Each representative of the flora kingdom evaporates impressive amounts of moisture. Water is necessary for plants to carry out life processes and is absorbed by them through root system. It is pumped along the stems into the leaves, from where it consequently evaporates. As shown Scientific research, plants absorb only 3% of the water supplied to them, and the rest evaporates.

The process of evaporation of water from the surface of plants is called transpiration. In fact, this is the ridding of a living organism from excess water, as well as an analogue of sweating in representatives of the animal kingdom. The main part of plants evaporates water from the back of the leaves, where there are special green cells (stomata), which form small gaps between themselves.

The role of water evaporation in plant life

• When a plant absorbs water, it absorbs various mineral components from the liquid. There are not very many of them in the water itself, so a large volume of liquid is driven through the stems per day. Gradually, due to root pressure, the water level in the plant rises, and it enters the leaves, from where it evaporates.
• By evaporating the liquid, the plant can cool itself. This is due to the effect of the maximum heat capacity of water. If a representative of the flora is in the sun for a long time, automatic transpiration begins, and water vapor carries away excess heat with it.
• Evaporation of moisture is also a necessity for plants, since water must rise to carry out various biochemical processes, such as photosynthesis.

For the environment, and in particular for humans, the evaporation of water by plants is also very significant. The intensity of this phenomenon, for example, reduces the nutritional value and taste of agricultural crops. The more often moisture evaporates, the poorer the soil becomes, constantly releasing water enriched with mineral components. Hence the need arises for regular improvement of lands and their fertilization.

The process of evaporation of water by a plant

As already noted, evaporation of water is possible due to the presence of stomata on the leaves. Their number in each organism is not the same and is determined by the habitat and characteristics of a particular representative of the flora (water level in the cells, age, osmotic pressure of cell sap). The intensity of moisture evaporation also depends on the presence of shade, air masses and the water level in the ground.

When a plant accumulates excess water, the stomata expand and their cells form holes from which water vapor escapes. In the intercellular spaces, the liquid is always in a state of vapor, but it can leave the leaf only when the stomata open. Typically, the process of transpiration occurs during the day when the stomata are automatically open. But if a plant suffers from drought, it changes its regime and minimizes water evaporation.

Plants that grow in warm climates, such as the tropics, always have large leaves so that the maximum amount of water evaporates from their surface in a short time. In cold or dry climates, the opposite is true. Also, if the plant is not interested in regularly getting rid of excess water, its leaves in the process of evolution become covered with a waxy coating or small villi. It is not uncommon for leaves to be curled in sunlight to reduce evaporation.

Angiosperms evaporate water not only from the return, but also front side sheet plates. This is due to the fact that the stomata are located on both sides, but the underside of the leaf is almost always in water and evaporation is impossible.

The level of humidity in the house plays a vital role in shaping the microclimate, providing a healthy and comfortable atmosphere, or, conversely, promoting the development of pathogens, mold growth, the proliferation of dust mites, causing allergies, emergence unpleasant odors and discomfort. An increased level of humidity in building structures, elements and materials, a reduced or absent possibility for natural or forced drying leads to permanent or temporary accumulation of moisture in the thickness or on the surfaces of materials, which can increase their thermal conductivity, accelerate corrosion or biological destruction.
Insufficient humidity levels in the house also lead to discomfort in the internal atmosphere of the house.

Optimal level Relative humidity in a home is considered to be between 30 and 50%. Relative humidity is determined by the ratio of the amount of water vapor in the air to its maximum possible content at a given temperature. The higher the air temperature, the more water vapor it can contain. The temperature at which the air cannot contain any additional water vapor is called the "dew point". A low level of relative humidity ensures maximum comfort for humans, does not contribute to the development of potentially harmful microorganisms (dust mites) and ensures the safety of building structures and materials.

Signs high humidity in the house.

Unpleasant odors. The intensity of odors in a room increases with increasing humidity. An increase in household odors may indicate an increase in humidity in the room atmosphere. A musty smell can signal the growth of mold, mildew, or rot.

Feeling damp. Indicates an increase in humidity and poor ventilation of the room.

Condensation, formation of frost and ice on cold surfaces. Condensation, frost, ice on cold surfaces indicate excess moisture in the room and the presence of insufficient insulation outer contour buildings and possible leaks of warm air through cracks.

Changes in color, texture and moisture content of material surfaces. Warping, swelling, deformation, cracking, blistering, crumbling, peeling, discoloration, darkening, the appearance of dark or colored spots or veins on the surfaces of materials may indicate increased humidity in the room. The growth of mold or mildew is accompanied by the appearance of spots of white, orange, green, brown, blue or black. Intensive reproduction of fungi begins at a relative humidity of 70%.

The formation of bubbles and paint cracks indicates capillary pressure of moisture in porous structures. The precipitation of salts and powdery substances on concrete surfaces is an indicator of the presence of moisture that has evaporated from the surface of the concrete. The formation of lamellar chips on the surface of concrete indicates the freezing of excess moisture in the thickness of the material.

Biological destruction of wood. Rot and decay of wooden structures indicates the constant damaging effects of moisture, which creates optimal conditions for the growth and reproduction of wood-destroying microorganisms. At biological destruction the wood changes its color, becomes loose and soft, which can lead to damage to the integrity of wooden structures under load.

Wet pipes.“Sweating” cold pipes are a sign of high humidity in the house. Current cold water significantly cools the surfaces of pipes on which excess moisture condenses.

Hygrometer readings. If the relative humidity in your home exceeds 50%, it may indicate a moisture problem. Moreover, even a low level of humidity in the atmosphere of the house does not guarantee the absence of problems with excess humidity in structures or separate rooms(basements, attics, etc.).

Sources of high humidity in the house.

1. Interstitial moisture. Porous building materials such as wood, concrete and others contain a certain amount of moisture located in the structure of the material. Moisture from materials can, under suitable conditions (the absence of vapor-proof barriers, an increase in the temperature of the material, the presence of a difference in water vapor pressure), begin to evaporate into the internal atmosphere of the house, increasing the humidity level. The volume of seasonal evaporation from building materials can reach from 3 to 8 liters of water per day. In internal environment In a newly built or renovated house, wet building materials evaporate on average up to 5 liters of water per day.

1. Trunk moisture. Moisture can enter the house in the form of rain, snow or groundwater, water supply and sewerage leaks, storage tanks for water, seeping through leaks in moisture-proofing media (roofing, walls, waterproofing, pipes, shut-off fittings, containers).

1. Capillary moisture. Capillary moisture enters the house through microscopic communicating pores of materials such as concrete, brick, wood from the external humid environment in the absence of waterproofing layers or layers that break the capillaries. Even the presence of a foundation slab is not an obstacle to moisture entering the house from the ground, if under the slab there is no layer of waterproofing and a granular mineral layer (coarse sand, crushed stone, gravel) that breaks the soil capillary network. The amount of moisture entering a house when the foundation waterproofing is damaged can be quite significant - up to 50 liters of water per day.

1. Moisture vapor transfer through porous materials. Due to pressure differences, water vapor can penetrate porous materials such as cellular concrete or wood. Both excess vapor transfer during outside-in steam transfer, for example, in hot and humid climates, and insufficient or blocked inside-out steam transfer can contribute to an increase in humidity. Significant moistening of building structures occurs when moisture evaporates from the uninsulated soil under the house, especially in the absence of sufficient ventilation of the underground space.

1. Moisture transfer with air flow. Air flows through cracks in building structures, on unsealed sections of media, around communications passing through walls and ceilings or open openings, windows or doors are capable of transferring saturated water vapor from the street. Up to 98% of all moisture enters the house with air flows. All other paths account for no more than 2% of the volume of moisture in the house. An uncontrolled influx of cold winter air containing a reduced amount of moisture can lead to the opposite effect: drying out the air in the room. Insufficient or absent exhaust ventilation helps increase the humidity level in the house. Moisture transfer with ventilation air flows allows you to quickly and effectively reduce the level of humidity in the house.

1. The human factor in the formation of moisture inside the house. A person himself evaporates a sufficient amount of moisture into the internal environment of a living space through breathing and sweating. A family of 3-4 people evaporates up to 200 ml of moisture per hour (4.8 liters in 24 hours). A lot of moisture is formed during economic, household and hygienic activities. At wet cleaning up to 150 ml of moisture evaporates per square meter of area. Cooking food for a family of 3-4 people during the day (breakfast, lunch and dinner) and washing dishes leads to the evaporation of up to 3 liters of moisture. Cooking with gas increases the amount of moisture by another 1 liter. Drying clothes indoors results in the evaporation of 4 to 6 liters of moisture. In addition to increasing the humidity in the house, drying clothes indoors causes residues to evaporate. detergents and an increase in villus in the air, which can lead to the provocation of allergic diseases. When taking a shower, 100 ml of moisture evaporates every 5 minutes. An increase in humidity in the house is caused by cooking in dishes without lids, a significant number of live plants in pots, open aquariums, and the use of air humidifiers.

From inside or outside? Capillary test. To determine the external or internal source of the formation of excess humidity and dampness on the walls or floor, a capillary test is performed:

1. Find an area of ​​damp wall or floor.
2. Dry it thoroughly using wipes and a hair dryer.
3. Cover the area to be examined with a sheet of vapor-proof plastic or film.
4. Carefully adhere the material to the surface with waterproof plumbing tape.
5. After 2-3 days, examine the sheet of plastic and the surface of the wall or floor underneath it. If moisture appears under the sheet, this means the capillary origin of the incoming moisture through the building structures. If moisture condenses on the outer surface of the plastic, the source of increased humidity is located indoors. If moisture is detected both under the leaf and on the leaf, this may mean that there are two ways of moisture entering at the same time.

Options for solving problems with excess humidity in the house.

Foundation and basement.

You can reduce the likelihood of moisture entering by capillary through the foundation in the following ways: drainage surface waters, lowering the groundwater level and waterproofing foundations and underground structures of the building.

The set of activities includes:

1. Installation of a system for collecting precipitation from the roof and discharging it to storm sewer. Closed system preferred drainpipes with the supply of precipitation directly to the storm sewer, without intermediate outflow of collected water onto the blind area or soil. At open system Drainage trays are installed on top of the blind area. If there is a system for collecting and draining precipitation from the roof, it must be regularly cleaned of leaves and other debris that can impede its operation.
2. Device ground slope away from the building. The minimum recommended slope width is 150 cm with a rise of 7 cm at the house, and the optimal width is 3 meters with a rise of 15 cm.
3. Wide waterproofing blind area around the building will help reduce watering of the soil adjacent to the foundation and basement. It is not necessary to arrange concrete blind area: you can use a more economical soft underground blind area made of waterproofing polymer-bitumen materials, hermetically connected by gluing or fusing to the surface waterproofing of the foundation.
4. Foundation waterproofing It is performed in the form of sticking or fusing polymer-bitumen waterproofing materials onto a concrete surface primed with a primer. Waterproofing is applied to all faces of the concrete surfaces of the foundation, and not just to the outside. You should not use roofing felt for waterproofing - its service life before cracking does not exceed 5-7 years. The installation of a vertical drainage membrane of the “Delta” type will help reduce the backwater of groundwater.
5. Device ring drainage around the foundation with water drainage lower along the terrain, or into drainage reservoirs or wells. It is recommended to triple at least two drainage rings - next to the foundation and next to the edge of the waterproofing area around the foundation.
6. When constructing a new building and laying the foundation and underground structures of basements, compacted cushions made of coarse sand, sand-gravel mixture or crushed stone(at least 10 cm thick) to reduce and break capillary pressure. Under the foundation slab, waterproofing material or expanded polystyrene slabs are laid, which have practically zero moisture permeability. All concrete structures, which will be located in the ground, are protected by several layers of waterproofing.
7. Installation protective plate-visor to protect against rain splashes and the penetration of insects along the entire perimeter of the foundation, covering the entire upper edge of the foundation, will significantly improve the waterproofing of walls from the foundation in addition to standard polymer-bitumen materials.
8. Do not store firewood on the blind area along the walls of the building - this impairs the ventilation of the foundation and walls, which can lead to increased moisture in the structures.

Underground.

During the construction of newly constructed buildings, it is better to avoid the construction of underground floors, as thermally and structurally irrational elements, replacing them with the construction of floors on the ground, or with a slab foundation. If you want to have an underground, or if there is an underground in an already existing building To control moisture entering through the underground, the following measures are carried out:

1. Soil insulation. The soil under the building within the foundation is covered with bitumen-polymer waterproofing material, thick PVC or butyl rubber film. The overlapping edges of the film are glued to the inner surface of the foundation. The sheets are glued together with an overlap of at least 15 cm. If there is a pile or pile-grillage foundation, the soil is covered without gluing the waterproofing to the piles. The waterproofing material in the underground is covered with a 10 cm layer of sand or a 5 cm thick screed to ensure its mechanical protection.
2. Adequate ventilation of the underground space. If there is no insulation of the soil under the building, vents with a total cross-section of at least 1/400 (requirements of the International Building Code - 1/150) of the underground area must be installed in the foundation. Vents should be located opposite each other to ensure cross ventilation and no further than 90 cm from the internal corners of the foundation. The minimum cross-sectional area of ​​one vent is 0.05 m2 (for example, 20 by 25 cm). If you have properly insulated soil, you can avoid vents in the foundation.

Walls

1. The minimum recommended height of the foundation or plinth under the outer part of the wall should be 60 cm. If the height of the foundation is less, then it is necessary to protect the wall with a splash-reflecting canopy, or install walls overhanging the foundation with waterproofing of the lower edge. Also the lower 50 cm of external walls are made of mineral materials, or with finishing made from them, can be protected from moisture with a calmatizing hydrophobic impregnation.
2. The walls to which the roofs adjoin can be protected with a layer of waterproofing and covered with a wall metal profile.
3. The lower parts of the external walls should not be covered with tall plants and firewood should not be stored nearby, as this impairs air circulation and the natural drying of the walls. In addition, deposits, reflected from objects near the outer walls, can land on areas of the walls less protected from moisture.

Particular attention should be paid hydro-vapor barriers around windows and doors. Windows should be equipped with drip sills that prevent droplets from flowing down the lower surface of the sill toward the walls. Most windows and doors are now installed using polyurethane spray foam. Polyurethane foam with an open cell structure is not an obstacle to vapor transfer and moisture penetration.

Therefore, immediately after hardening, the polyurethane foam should be covered with a vapor barrier tape on the inside and a waterproofing, vapor-permeable tape on the outside. To seal gaps, you can use pre-compressed self-expanding sealing tapes - PSUL. It is better to additionally insulate the slopes around windows and doors to prevent them from cooling and the formation of condensation.

Exterior decoration and curtain facades on the walls.

The basic rule for constructing multilayer walls to prevent their overmoistening is formulated in paragraph 8.8 of SP 23-101-2004 “Design of thermal protection of buildings”: To ensure better performance in multi-layer building structures, layers of greater thermal conductivity and greater vapor permeability resistance than the outer layers should be placed on the warm side. This means that the materials exterior finishing should not interfere with natural vapor transfer through wall materials. This situation can arise when externally covering vapor-permeable wall materials, such as autoclaved aerated concrete, with vapor-tight insulation, brickwork, plasters and paints, or installing suspended vapor-tight facades without ventilation of the gap between the walls and the facade.

Flat ledges on the walls, not equipped with protective canopies or slopes to drain water, ledges with a negative slope on the walls are a place for precipitation to collect, with subsequent moistening of the walls and the penetration of moisture into the house by capillaries. Uncleaned gutters result in overflowing water hitting the walls.

Internal vapor barrier of walls. The main purpose of internal vapor barrier is to reduce or prevent vapor transfer through vapor-permeable wall materials. The installation of proper vapor barrier is especially important for preserving the properties of porous, cellular and fibrous thermal insulation or structural thermal insulation wall materials. When moisturized thermal insulation materials their thermal conductivity increases exponentially. The main mistake made when installing a vapor barrier is the lack of sealing of the joints of sheets of vapor barrier materials and their abutments to walls and structures. Be sure to seal any holes or punctures in the vapor barrier that may occur during construction. The vapor barrier material itself can only withstand the diffusion transfer of moisture. However, as is known, 98% of moisture is transferred not by diffusion, but by air currents. In the presence of microgaps and cracks in joints and abutments, the effectiveness of vapor barrier is significantly reduced, and the risk of moisture in wall materials increases significantly. A continuous additional layer of vapor barrier plaster or paint on internal surfaces premises will reduce the risk of dampening the walls from internal sources of moisture.

Cold attics. The main source of moisture in the attic is the penetration and leakage of air from the underlying premises through leaks in the attic floor. To ensure normal humidity conditions the attic must be well ventilated through ventilation openings in the gables, dormer windows. It is recommended that at least half of the ventilation openings be 1 meter higher at the ridge in relation to the rest. IN hip roofs Ridge ventilation must be provided. To prevent condensation, all ventilation and chimneys must be insulated. It is prohibited to vent the exhaust ventilation of premises into the attic space.

Warm attics. The main mistake when installing warm roofs is insufficient ventilation gap, lack of ridge ventilation and blind filing of overhangs, blocking under-roof ventilation. Existing ridge vents, roof fans and soffit perforations can become clogged with plant pollen, cobwebs and leaves, which leads to poor ventilation of the under-roof space of warm roofs.

Control of internal moisture sources.

A significant contribution to the increase in humidity can be made by open or hidden (in walls, ceilings, underground, ground) leaks of water pipes and sewers. You can determine the presence of a hidden water supply leak using a water flow meter, which will show water consumption when there is no consumption.

It is necessary to provide for drying clothes on outdoors, either in dryer. Open aquariums can be closed with a lid. A supply of firewood should be stored in the house for no more than 1-2 days. When a large number of people live in a small room, you can use a mechanical dehumidifier.

Conclusion.
You should think about controlling humidity in a house at the stage of its design, providing all the necessary structural barriers for the penetration of moisture into the house and its structures, both outside and inside. The layout of the house, the location of windows and doors, elements of natural and forced ventilation should promote effective air exchange and removal of moist air.

A thoughtful analysis of the causes of high humidity in an already built house will help you make the right decision about possible ways to solve problems with excess humidity.

Every day, the skin of every person is influenced by various negative factors, such as weather conditions, the environment, and the ecological situation in the region of residence. Most negative impact The skin is exposed to ultraviolet rays when exposed to the open sun or during normal tanning. But important Air humidity also has an effect on the skin, since there are many subtleties here.

Humidity and skin

Of course, every person has noticed that on hot days and dry weather, as well as when exposed to dry wind for a long time, one becomes very thirsty. The body at this time requires a large amount of fluid, as it loses water due to external natural factors and needs to replenish these losses.

However, even when drinking large volumes of liquid in the presence of dry air, skin cells do not have enough moisture to function normally, since it evaporates in large quantities through the skin.

Air humidity is a certain indicator of the amount of water contained in it. This indicator is of particular importance for the general condition of a person and his skin, and also affects the degree of comfort of being indoors or outdoors.

For example, in the summer, on the hottest days, most people find it very uncomfortable to be outside because it is difficult to breathe. This is explained by the fact that when heated, the air is saturated with moisture (its evaporation from the surface of reservoirs and soil), and the higher the air temperature, the greater the volume of water it can absorb. As a result, on hot days, especially if it has rained before, people experience serious discomfort and breathing problems. Of course, this condition also affects the skin, since the heat causes increased sweating, which can lead to serious fluid loss.

About the same thing happens in winter, when outside very coldy. During this period, air humidity usually decreases, since due to the low temperature water does not evaporate, but at the same time the air is also ready to accept moisture and absorb it. As a result, in the cold it is very difficult to breathe due to the dry air. With breathing, a lot of steam comes out, the molecules of which are immediately absorbed into the air. As a result, the body loses large volumes of water. The air takes water away from the skin of the face, as well as from other open areas of the body. That is why, after a long stay in the cold, as well as in the heat, the skin becomes dry and dehydrated.

As a rule, if the air temperature is high, but the air humidity is low, people tolerate it much more easily and have less impact on the condition of the skin. At low temperatures accompanied by high levels of air humidity, rapid hypothermia can occur.

What are the dangers of violating the humidity level?

The most comfortable indicators of air humidity for a person’s condition, his health and maintaining the correct water balance in the body and skin cells is a value from 30% to 60%. If the indicators deviate in any direction, this can lead to various negative consequences.

At low air humidity, due to strong evaporation of moisture, the skin very quickly dries out, becomes dehydrated, and begins to peel and crack. As a result, damage to the skin appears, which is not always noticeable to the eye, but, nevertheless, allows free access to the body for a variety of pathogenic microorganisms that can provoke the formation of an inflammatory process and acne, as well as infection with serious diseases.

In addition, when too high humidity in the hot season, the body sweats intensely, trying to cool the skin and protect it from overheating, not only losing water, but also forming a sticky film on the surface of the skin, to which dust and other contaminants stick. As a result, not only dehydration of the skin may occur, but also a large number of acne caused by blockage of pores and sebaceous ducts.

If the air humidity is high, the body begins to lose heat simultaneously with intense sweating, resulting in a serious risk of overheating. In this case, not only the human skin suffers, but the entire body. With prolonged stay in rooms with high air humidity, a person may experience a general decrease in immunity, which results in not only skin diseases, but also various diseases internal organs, and exacerbation of existing diseases occurs.

Of course, it is impossible to say unequivocally that when the level of air humidity increases or decreases, a person will definitely develop skin problems, since each organism is individual and its reaction to certain environmental changes is simply impossible to predict. Skin reaction different people changes in the environment will be different, while if a certain level of air humidity has a positive effect on the skin of one person, then it may be negative for the skin of another person.

For example, with dry skin, a high level of air humidity will be useful, since the water in the air will become an additional source of hydration of the epidermis. A low level of humidity with dry skin will provoke the appearance of peeling and dehydration. In addition, humidity helps smooth out wrinkles. However, if you have oily skin, high humidity levels can be a factor in causing acne. Therefore, quite often the condition of the skin depends on the air humidity in the apartment or other room.

In most cases, in winter, the air in apartments and houses has a low level of humidity, which is facilitated by the operation of various heating devices. As a result, the skin becomes drier, thinner, and may show signs of aging. Therefore in winter period the skin needs additional care, hydration and nutrition. It is also recommended to humidify the air in the apartment, using special air humidifiers or simply placing containers with clean water, the evaporation of which will provide additional humidity.

As a rule, in order to avoid undesirable consequences and complications, cosmetologists recommend adjusting to a certain level of air humidity, providing the skin the necessary conditions. At low humidity levels, the skin must be treated with creams and other products for deep intensive hydration and nutrition. Such products have a fairly dense structure, and their use helps prevent dehydration. However, when high level Humidity should also not be forgotten about hydration, especially in the summer. But creams with a dense structure are not suitable here. In summer, it is best to use moisturizing gels that quickly penetrate the skin and do not create unnecessary heaviness.

Video about dry air in apartments

A. Margolina, E. Hernandez. "New cosmetology".

Moisturizing creams are a cosmetologist's magic wand.

A lot depends on the moisture content of the skin - its elasticity, firmness, even color. Just by moisturizing the skin, you can completely smooth out fine wrinkles, disappear dark circles under the eyes, and give the skin a lighter shade. It’s no wonder that cosmetic companies are actively using this optical effect. Many anti-wrinkle products are nothing more than well-formulated moisturizers. There would be nothing wrong with all this if cosmetics manufacturers sometimes did not use prohibited techniques, namely, they did not simultaneously include in cosmetic products substances that increase skin permeability (the simplest is sodium lauryl sulfate) and substances that slow down the evaporation of water.

On the one hand, due to the slight swelling that occurs after such remedies, wrinkles magically disappear, the face brightens and acquires youthful swelling. However, systematic use of such products over a long period of time can cause harm to the epidermal barrier. Therefore, if a product produces an instant effect, transforming your face literally before your eyes, it is better not to use it every day, but to put it aside for those occasions when you need to look good.

On the other hand, by maintaining the required level of moisture in the skin, we prevent aging changes, create conditions for the normal functioning of all skin structures, and strengthen its protective properties. And this is no less (if not more) important than periodic “stimulation” of the skin and active interference in its vital functions.

Ways to increase skin moisture.

Slowing down evaporation (occlusion).

Water continuously rises from the depths of the skin to its surface and then evaporates. Therefore, if you slow down its evaporation by covering the skin with something gas-tight, the water content in the epidermis will increase quite quickly. This method is called occlusal(from the English occlusion - barrier, barrier).

If the film is completely impermeable (for example, plastic film), then the epidermis will become too wet, which will lead to swelling of the stratum corneum and destruction of the barrier. Rubber gloves and breathable clothing also lead to overhydration. In such cases they say that “the clothes don’t breathe.”

Semi-permeable film, which only slows down but does not completely stop the evaporation of water, will also eliminate the symptoms of dryness without damaging the skin.

Ingredients that slow down water evaporation include:

• Mineral oils, petroleum jelly, liquid paraffin, cesarine - all these are hydrocarbons, petroleum products;
• Lanolin (from Latin lana - wool, oleum - oil) is an animal wax obtained by refining wool wax (it is extracted organic solvents from sheep wool);
• Animal fats – goose fat, whale oil (spermaceti), pork fat;
• Squalene and its derivative squalane (from the Latin Squalus - shark) are a natural component of human sebum; sources of production are different (for example, shark liver, some plants);
• Vegetable oils– mostly solid, for example, shea butter (shea butter);
• Natural waxes and their esters – beeswax, vegetable waxes (coniferous reed, etc.).

The above components vary in occlusion strength. Vaseline is considered the most reliable proven moisturizing component. In dermatology, it is used to moisturize the skin for eczema, psoriasis, atopic dermatitis and other diseases. Disadvantages of Vaseline and other derivatives mineral oil is an unpleasant feeling of heaviness and fatness.

Because Vaseline is too moisturizing, it can slow down the repair of the epidermal barrier - the cells will not receive a signal in time that the barrier needs repair.

Occlusive moisturizers (i.e., those that block the evaporation of moisture) quickly eliminate dry skin, reduce inflammation and itching in skin diseases, but they do not act on the cause of skin dehydration. They can be compared to crutches, which are necessary for those who cannot move independently, but are completely unnecessary for people with normal legs.

If the skin barrier function cannot be restored, occlusive creams are necessary. If there is a chance for recovery, they should be used only at the initial stage.

There are several categories of cosmetics used when the use of occlusive components is justified. For example, post-peeling care products applied to skin with a damaged barrier after peeling. In such cases, occlusive drugs act as an “ambulance”, maintaining the level of moisture necessary for normal cell functioning during the most acute period.

Children's cosmetics for skin care in the diaper area, where the skin is constantly irritated, should have occlusive properties.

Hand protectants also include occlusive ingredients. No part of the body is subject to such strong attack from the external environment as the hands. The skin on them is constantly injured, even everyday washing with soap (not to mention contact with products household chemicals), containing surfactants, damages the lipid barrier. Applying an occlusive agent will prevent the skin of your hands from drying out and soften it.

It should be noted that almost any moisturizing cream contains components that reduce evaporation due to occlusion. But if in some preparations this is the main component, then in others it is an auxiliary component, and the main role is given to substances that absorb and retain moisture.

Trapping moisture.

The use of substances capable of binding and holding water molecules (such compounds are called hygroscopic) - wonderful way quickly moisturize the skin. In cosmetics, two categories of hygroscopic compounds are used, acting on the skin in two different ways.

"Wet compress" method.

Some substances adhere to the surface of the skin and absorb moisture like a sponge, forming something similar to a wet compress. This effect is achieved by:

• Glycerol;
• Sorbitol;
• Polyglycols (propylene glycol, ethylene glycol);
• Polysaccharides – hyaluronic acid, chitosan, polysaccharides of plant and marine origin (chondroitin sulfate, mucopolysaccharides), pectins;
• Protein molecules and their hydrolysates (in particular, the popular cosmetic ingredients collagen and elastin are included in cosmetics precisely as moisturizing agents);
• Polynucleic acids (DNA) and their hydrolysates.

This list, among other things, contains substances with large polymer molecules (more than 3000 Da), which, due to their size, are not able to penetrate the stratum corneum.

The listed components are found in almost all cosmetic forms, including emulsion (creams). However, most of them are in gels and “liquid” products (tonics, lotions, serums, concentrates).

And now attention: the use of products that moisturize the skin like a “wet compress” is not always justified.

For example, in dry climates, when the relative water content in environment lower than in the stratum corneum, the compress begins to “pull” water from the skin. As a result, the stratum corneum becomes drier.

On the contrary, at high air humidity, applying cosmetics with these components actually softens and moisturizes the skin. At the same time, the appearance of the skin also improves - it acquires a matte shine, is slightly tightened and smoothed.

By the way, it is thanks to drying that the “compress” has a smoothing effect. High-molecular compounds that adhere to the skin and form something like a mesh on it, themselves compress and pull the skin along with them. The result is a “superficial lifting”, which is declared in the annotations of such cosmetic products. The severity of superficial lifting depends on the degree of drying: the drier the compress, the stronger the lifting (up to the appearance of a feeling of tightness characteristic of dry skin).

To prevent the rapid evaporation of water from the “wet compress,” substances that act as occlusion are added to cosmetic products.

Another option is to use a complementary pair, for example, a moisturizing toner plus a cream. Consistently applying toner first and cream on top will help soften the skin and retain moisture for a longer period.

Note that in professional cosmetics they prefer the second option, because it gives more opportunities in terms of an individual approach to the skin different types and taking into account climatic features.

Method of “Deep” skin hydration.

Some cosmetic products say that they have the effect of deeply moisturizing the skin. What does this mean?

A common misconception is to think that all layers of the skin, including deep ones, are moisturized. In fact, only the stratum corneum is moisturized.

The role of natural sponges in the stratum corneum is played by the components of natural moisturizing factor (NMF) - free amino acids, urea, lactic acid, sodium pyroglutamate. They are located throughout the stratum corneum, and only in it.

Rice. Water-retaining structures of the stratum corneum.

These compounds are formed as a result of the breakdown of proteins (mainly filaggrins) that provide adhesion to the cells lying under the stratum corneum. Having passed into the stratum corneum, the cells not only lose their nucleus, the connections between them are also gradually destroyed (which is why the horny scales that are not attached to each other freely peel off from the surface of the skin).

NMF molecules are located in close proximity to corneocytes. A significant portion of the water present in the stratum corneum is associated with NMF. Bound water participates in the gluing of horny scales and, along with sebum, ensures the plasticity and smoothness of the skin surface, however, does not interfere with the disintegration of the scales and their natural removal.

Unlike large high-molecular compounds, NMF components applied as part of cosmetics can penetrate into the thickness of the stratum corneum (but not deeper) and increase its moisture-retaining potential. The hydration that is felt in this case, as a rule, is not as pronounced and does not occur as quickly as with the “wet compress” type, but it lasts longer and is less dependent on air humidity. There is no lifting effect observed.

Substances that absorb and retain moisture best moisturize the skin either humid air, or if they are applied directly after taking a bath or shower. They increase the plasticity of horny scales and reduce the roughness of the skin surface. However, they do not reduce skin irritation or create the same firmness and freshness as occlusive agents. Therefore, in cosmetic formulations they are usually combined with occlusive components.

Restoration of damaged lipid barrier.

Damage to the barrier is one of the causes of dryness.

Damage to the lipid barrier of the stratum corneum (changes in lipid composition, structural changes, destruction) is one of the most common reasons dry skin. The main indicator that the barrier is broken will be an increase in the transepidermal water loss index (TEWL).

Even if a violation of the lipid barrier is not the root cause of the development of dryness, it still occurs if the skin long time suffers from lack of moisture. Therefore, in addition to using moisturizers that relieve the feeling of dryness and increase the moisture content in the stratum corneum, it is necessary to use products designed to restore the barrier.

First of all, damage to the barrier should be patched up fairly quickly with something. For this purpose, lipids are used, both in the form of pure oils and in combination with other ingredients in local preparations.

Lipid molecules penetrate into intercellular spaces and are integrated into the lipid barrier. Some of the lipid molecules applied on top gradually move along the intercellular spaces, reach the living layers of the epidermis and are included in cellular metabolism. In particular, they can serve as a substrate for further lipid synthesis, which is characteristic of the skin barrier.

Substances used to restore the barrier.

Natural oils are mixtures of lipids. Therefore, the restorative efficiency and preferential mechanism of action of oils will depend on their lipid composition. Oils containing essential fatty acids (linoleic and gamma-linoleic) promote accelerated synthesis of lipid barrier components, delivering the necessary lipid precursors directly to the cells (borage oil, evening primrose oil, seeds black currant).

Oils enriched with saturated and monounsaturated fatty acids have more pronounced occlusive properties and help restore barrier properties by hydrating the epidermis (shea butter, lard, macadamia, corn, coconut, cocoa, cashew).

Lipid mixtures composed of physiological lipids - ceramides, cholesterol, and free fatty acids - are very effective. These lipids are called physiological because they constitute the natural lipid barrier of the human stratum corneum. It was experimentally established that their equimolar (i.e. in equal parts) mixture – “ceramides/cholesterol/free fatty acids”—has the best restorative properties.

Micelles, liposomes, lamellas.

It is no coincidence that lipids are one of the most popular cosmetic ingredients. They can be included in formulations both as individual molecules and as structural formations. The latter include, for example, liposomes and micelles. In addition to the traditional role assigned to lipids, such structures act as carriers or containers for other biologically active components, stabilizing them and facilitating penetration through the stratum corneum.

A relatively new technology in cosmetics is the use of so-called lamellar emulsions based on phosphatidylcholine (lecithin), in which tiny drops of lipids are stabilized not by conventional emulsifiers, but by a network of biolayers, similar to those that make up the lipid barrier. “Preparations that are structurally appropriate to the skin” is how these cosmetics are often called. They have excellent moisturizing and restorative properties, since they are compatible with the lipid barrier not only in composition, but also in structure, which is especially important in the case of dry or sensitive skin.

Skin with increased permeability is characterized by increased sensitivity to toxic and irritating influences. Therefore, until its barrier layer is restored, it needs protection.

To protect the skin from damaging effects, film-forming substances and antioxidants are used. Good protection for the skin provide biopolymers that form a semi-permeable film on the surface of the skin. These are, first of all, natural polysaccharides - chitosan and hyaluronic acid.

Protecting the lipid barrier from oxidation

Along with mechanical protection The lipid barrier of damaged skin must be protected from peroxidation. To do this, antioxidants are introduced into cosmetics - substances that neutralize free radicals and break oxidation chain reactions.

The most common cosmetic antioxidant is vitamin E, which easily penetrates lipid layers (since it is fat-soluble) and protects them from oxidation.

Water-soluble antioxidants are also used - vitamin C and bioflavonoids (plant polyphenols).

Barrier restoration sequence.

Creams that create a temporary barrier on the surface of the skin partially eliminate the consequences of damage to the epidermal barrier and prevent the development of pathological reactions, but they do not accelerate, and sometimes (especially when long-term use) even slow down the process of barrier restoration.

In order to bring the skin to normal condition, it is necessary to achieve complete restoration of its structure and functions. If the skin has everything necessary for the synthesis of endogenous lipids (precursor lipids and enzymes), the barrier is completely restored within three days. Otherwise, the skin will need additional help.

Now that the first stress caused by damage to the epidermal barrier has passed, you can apply fatty components (lipids) that will penetrate deep into the skin, supplying the cells with the necessary building material.

Since skin cells have everything necessary to disassemble fats into their component parts, there is no fundamental difference in what kind of lipids will be used - the main thing is that they contain the necessary components.

Most often, oils containing essential fatty acids - linoleic, linolenic, gamma-linolenic acid (GLA) - are used to supply the skin with building material. They are used both in cosmetics and in the form of food additives. Oils rich in GLA, such as black currant seeds and borage, have a particularly beneficial effect on the skin.

It should be remembered that the process of skin restoration occurs slowly. Therefore, the effect of using Vaseline, emollients and moisturizers will be more noticeable than the effect of using creams containing essential fatty acids.

Since polyunsaturated fatty acids cannot be a means emergency assistance When the barrier is destroyed, they must be taken regularly to prevent the occurrence of deficiency conditions.

Roughness of the skin, a feeling of tightness, irritation - all this can be relatively quickly eliminated with a combination of emollients. For this purpose, formulations are used that, on the one hand, have average or low spreadability rates (i.e., do not spread well on the skin and are perceived as quite greasy), on the other hand, they must have average absorption rates. In other words, they should be felt on the skin for some time in the form of a thin fatty film.

Emollients (including many oils) somewhat limit the evaporation of water and therefore, like occlusive agents, increase the moisture content of the skin. In addition, they soften the skin and smooth out the horny scales, improving the appearance of the skin. Emollients, strictly speaking, are not moisturizers, since they have little effect on the moisture content of the skin, but they help to significantly reduce the discomfort caused by dry skin.

Irritation from using moisturizers.

Although moisturizers are supposed to reduce skin irritability (i.e. increase its sensitivity threshold), in real life many of them have a direct opposite action. This is explained by the fact that when the stratum corneum is oversaturated with water (this condition is called hyperhydration), it becomes more permeable, which means that substances that previously did not pass through it can pass through it. Therefore, it is necessary to ensure that moisturizers contain as few substances as possible that could potentially cause skin irritation.

Here is a list of some of these substances:

This list is not complete, since, according to the literature, skin irritation can also be caused by propylene glycol, phenoxyethanol, preservatives that release formaldehyde, almost all essential oils and many other components. That is why, when buying a moisturizer for sensitive, irritation-prone skin, you need to choose one whose formulation contains as few ingredients as possible. If you have a product with 40 or more components, the likelihood that your skin will not like some of them is very high.

Dry skin and nutrition.

It has been repeatedly noted that the skin is not a digestive organ, therefore, it is not so easy to “nourish” it from the outside. Many substances must necessarily pass through digestive system and be exposed to a wide variety of enzymes before they can be used to feed body cells (and skin cells are no exception). Therefore, along with the use of cosmetics that replenish the deficiency of essential fatty acids and antioxidants, it is useful to make changes to the diet.

This means limiting the consumption of meat and fatty poultry, as well as chips, hamburgers, etc. Instead of meat, you need to learn to eat fatty fish, such as salmon, cod, mackerel. Fish is a source of valuable omega-3 fatty acids, which are necessary to restore the balance of the body's immune system. However, it must be borne in mind that now many species of large predatory ocean fish are recognized as not completely safe for health due to the fact that mercury and other toxins can accumulate in their meat.

Cabbage and carrot salad with butter, fruits (citrus fruits, apples, etc.), and berries (sea buckthorn, blueberries, grapes, etc.) are used as a source of antioxidant vitamins.

Although everything useful material best received as part of food products, rather than in pill form, it is sometimes worth supplementing your diet with nutritional supplements containing essential fatty acids and antioxidant vitamins.

Dry air means dry skin.

One of the most effective ways to combat dry skin is to increase air humidity. It has been experimentally shown that prolonged exposure to dry air leads to damage to the barrier function of the skin, which leads to the development of dry skin.

You can increase air humidity in different ways - buy a humidifier, cover the central heating radiators with a damp cloth, place containers of water, plants with large leaves or an aquarium in the room.

If it is possible to regulate the temperature in the room, then you need to maintain it at a minimum comfortable value.

If dry air is unavoidable, then after each wash or shower, apply a moisturizer to still damp skin.

Moisturizing for skin diseases.

Many skin diseases are accompanied by dry skin. Dermatologists have long noticed that the use of emollients and moisturizers reduces discomfort in a number of skin diseases and even extinguishes the inflammatory reaction.

However, only recently have moisturizers and emollients been recognized as an important aid to the dermatologist in the treatment of skin diseases.

In many skin diseases, the skin is not able to form a complete epidermal barrier, so it does not retain water well and easily allows allergenic and toxic substances to pass through.

In itself, increased evaporation of water through the stratum corneum is already an alarm signal for cells, by which they begin to release signaling molecules, many of which are capable of igniting a fire of an inflammatory reaction in the skin.

At the same time, the systematic use of products that normalize the evaporation of moisture from the skin and create a temporary barrier extinguishes this fire and allows the skin to function normally even with a broken barrier.

Since when the barrier is damaged, the skin is obviously highly reactive, the formulations of cosmetics for people whose dry skin is caused by skin diseases should be the simplest, i.e. contain as few components as possible. In the very simple version this can be well-refined petroleum jelly (it used to be lanolin, but then, due to reports of allergic reactions to lanolin, it was largely abandoned).

There are dermatological compositions containing a suspension of phospholipid liposomes or lamellar emulsions, prepared using a special technology without surfactants, fragrance additives and preservatives.

Moisturizing is a vital part of the corneotherapy approach to solving skin care problems. Its essence is that it is enough to put the stratum corneum in order and maintain it to prolong the youth and health of our skin, help it cope with various skin diseases (if any) in whole or in part, reducing discomfort.

Choosing a suitable moisturizer is not an easy task, and often it cannot be solved immediately, focusing only on the external signs of dry skin. Until recently, choosing a moisturizer was a matter of trial and error. Now, with the advent of special equipment in beauty salons, it is possible to accurately determine the leading link in the pathogenesis of dry skin in a given person and, based on this information, select an individually suitable moisturizer.