Does the skin absorb water? How the cream penetrates the layers of the skin. The mechanism of penetration of cosmetics into the skin

Of course, stress, the external environment, irrational and malnutrition - these are the main factors that can affect the condition of the skin. This is especially noticeable on the skin of the face. Of course, it is practically impossible for us to change the environment, and stress is also unlikely to be avoided. Every woman should strive to eat right, but even here the rhythm of life dictates its own rules to us.

In order for the skin of the face not to become a mirror of an unfavorable environment and stress, it needs care and special nutrition. Does the skin know how to take vitamins through itself, so that it can be nourished not only from the inside? There is no doubt that the skin absorbs the nutrients that we offer it through cosmetic preparations. A simple proof of this is the different reaction of the skin to cosmetics.

But in practice, it is much more important to understand not only whether the skin can take vitamins through itself, but also the amount of vitamin “feeding” that the skin needs. Can cosmetics, even in combination, provide the skin with all the substances that it needs? And will such richly fortified preparations be found on the shelves of cosmetic stores. The choice of even the most correct cosmetic products will not be able to solve the problems of skin nutrition in all their diversity. External nutrition of the skin must be supplemented with the correct "cosmetic" diet. It is not so difficult, because it is quite versatile, suitable for you and other family members. The principles of a balanced diet are a way of life. Even after a month of proper, harmonious nutrition, you will notice obvious positive results. However, if you violate the principles of nutrition, you will just as quickly notice reverse progress.

Can the skin take vitamins through itself? Certainly, and when combined with meticulous skin care with its internal nourishment, the deep skin cells that you nourish through proper nutrition will turn into a beautiful, healthy young layer of skin. Our skin needs all kinds of nutrients. Vitamin C will help collagen synthesis. Collagen is the basis of connective tissue, it guarantees skin elasticity, provides the necessary strength of blood vessels. Vitamin A makes the skin supple. To replenish the reserves of this vitamin, carrots will be extremely useful, as well as milk, eggs, and liver. Vitamin E is valuable for its ability to protect our skin from negative ultraviolet rays, stimulates the renewal of our skin cells. By the way, vitamins A and E can enhance each other's action. And you can find vitamin E in sunflower or soybean oil, eggs, milk.

Genuine leather is an incredibly durable material used for the production of clothing, footwear and accessories. Leather items are expensive. Many manufacturers offer shoes and accessories from more affordable leatherette. Things made of this material are visually similar to real leather. For this reason, the question becomes relevant: "How to check the skin for naturalness when buying?".

Surface inspection

The choice of any leather product, start with a close inspection of it. Natural without bends and wrinkles, any deformations can appear only in the process of prolonged wear. Study the relief and surface pattern. One of the easiest ways to check the skin for naturalness is to carefully examine the pores. On leatherette, they will be even and the same. While genuine leather has a unique pattern. Our mothers believed that the best way to calculate leatherette is to smell the product. But today, natural leather is subjected to complex processing. Some types of impregnations kill and mask the natural smell. And yet, natural haberdashery leather cannot have a pronounced, irritating chemical aroma.

Attention to detail: checking the inside and seams

Examine the places of bends and the edges of the product. Real leather is homogeneous, does not exfoliate. Still wondering how to check the skin for naturalness? Try to find an opportunity to look at its wrong side. Genuine leather will have a fleecy surface. Try to stroke the inside, traces will remain on it - these are the villi that have changed their direction. If the wrong side of the product is woven, it is definitely leatherette in front of you. One of the qualities haberdashery leather possesses is elasticity. Try to bend or wrinkle the product, when you straighten it, there should not be any folds or wrinkles. Pay attention to how the item you like is packaged. Genuine leather manufacturers do not save on beautiful boxes and protective wrappers. Very often, a sample of the material is offered for quality assessment of leather products. Studying it is another way to check the skin for naturalness. If the sample has the shape of a regular rhombus or rectangle, it demonstrates the quality of leatherette. Pieces of irregular shape are attached to products made of genuine leather, symbolizing the skin taken from the animal.

Checking patent leather

Patent leather products look stylish and bright. How to determine the naturalness of this material? Patent leather, like matte, is quite elastic and elastic. Try to crumple the product and straighten it, there will be no wrinkles and bends on the natural material. Place your hand on the surface of the material. Real leather will keep you warm. Natural material absorbs moisture, while water droplets remain on the surface of the artificial one. However, this method, how to check patent leather for naturalness, can be considered outdated. Today, leather is often treated with special compounds that make it waterproof. A specific test method is to put your hand on the surface of the product. The artificial polish should make your palm sweat.

Does real skin burn?

One of the most popular options for checking the naturalness of a leather product is to expose it to a flame of fire. Do not know how to check the skin for naturalness with a lighter? It's very simple - set fire to the product in an inconspicuous place. Leatherette will melt, while genuine leather will remain in its original form. This method is suitable for home testing. You can determine what a product sold as leather is made of by piercing it with a needle. The sewing tool will fit into leatherette with ease. Genuine leather is denser, it will not be easy to pierce it. Before buying, evaluate the uniformity of coloring of the material. Expensive real leather should have an even, pleasant shade. Drawings and sticker prints can be applied to natural material. If you like just such a product, check it in a place where only background paint is present. And the most important sign of quality: genuine leather cannot be too cheap. Even at sales and discount stores. The production of leather products and the pre-treatment of the material have a high cost. It is on its basis that the market price of clothing and accessories is formed.

Dermal absorption of essential oils (or lack thereof)
Cilla Sheppard Hanger
Martin Watt

Do essential oils pass through the skin into the bloodstream?

This question is associated with a lot of confusion and misinformation in the aromatherapy literature, as most sources state that the skin easily allows essential oils to pass into the bloodstream, and that significant amounts of essential oils enter the body in this way. They argue that this is due not only to the fact that the skin is the largest organ in the human body, but also to the fact that some essential oils have pronounced lipophilic qualities, and the size of the molecules of essential oils is extremely small.

Research confirms the ability of several drugs in the form of patches to penetrate the skin, and it is widely believed that essential oils have the same property. However, after reviewing the wide range of dermatological literature, it is easy to find strong evidence to the contrary. Whole essential oils don't have the ability to be easily absorbed through the skin, and only a few components of essential oils penetrate the skin into the bloodstream. Most of the chemicals found in essential oils enter the bloodstream in reasonable amounts through the mucous membranes of the nose and lungs, provided that essential oil vapors are present in the atmosphere in significant concentrations.

Through evolution, the human skin has evolved into a highly effective barrier. There is very little evidence that plant-derived fat-soluble substances can be absorbed into the skin, with few exceptions. With almost no exceptions (with the possible exception of chamazulene), the few chemicals that are able to penetrate the skin to a small extent are also widely known to cause an adverse skin reaction. It seems to us that this means that most essential oils, entering the body through the skin, are perceived by the body as hostile and alien elements. However, an important question remains uncovered: is essential oil able to penetrate into the body in sufficient quantity for any pharmacological action? And despite the lack of a clear answer to this question, aromatherapy works! This means that the problem is not with aromatherapy, but with misconceptions about how and why it works. Of course, the external application of essential oils on the upper surface of the skin works to treat some symptoms (including as an antiseptic, anti-inflammatory agent, etc.) and, in some cases much more importantly, aromatherapy affects our consciousness.

Based on theoretical models of how our skin works and works, some have suggested that essential oils can overcome this reliable barrier. However, the ability of the skin to pass whole essential oils has not yet been reliably confirmed. It is assumed that at least in theory that low molecular weight substances can penetrate the skin. The molecular weight of most essential oils and their natural components is less than 1000 m (m=molecular weight). It is often stated that "due to their lipophilic nature, some essential and fatty vegetable oils have an affinity (high affinity) to the skin, allowing them to penetrate the skin barrier and enter the bloodstream." It is also often said that "due to their lipophilic nature, essential oils are fat-soluble, and some oils (high in ketones) that have fat-dissolving properties [allegedly] can also dissolve the myelin sheath around nerves, causing neurotoxicity."

First, if essential oils were able to penetrate into living cells in sufficient quantities to dissolve fat, such an oil would also inevitably kill these cells. A test promoted by many, during which a drop of thuja essential oil ( Thuja occidentalis) applied to a clot of chicken fat and dissolving it before our eyes, cannot be considered "evidence" and in no way can be compared with the traditional use of essential oils in aromatherapy (might as well be considered evidence of how a drop of lavender oil over time "eats" a hole in a plastic cup).

Numerous references to the skin absorbability of medicinal patches, as well as garlic rubbed into the skin of the legs (the smell of which then manifests itself in the breath), are also not reliable evidence. The closed application (as a patch or compress) of concentrated chemicals cannot be compared to the use of essential oils in aromatherapy. Garlic is fundamentally different in its chemical composition from all essential oils. Due to the phenomenal volatility of essential oils, it is almost impossible to avoid inhaling them (to the point that many people hurriedly leave the room in which an open bottle of essential oil is located). Yes, oil enters the body, but mainly through inhalation and subsequent exhalation. Despite all of the above, there is still no strong evidence that the whole essential oil (rather than its individual components) in clinically active concentrations enters the bloodstream as a result of skin application, has not yet been received.

Secondly, for skin application, we always use carrier oil; Vegetable fatty oil molecules are much larger than essential oil molecules and, despite their lipophilic nature, are also unable to penetrate the skin (1). The theoretical model mentioned above insists that the skin is relatively easy to absorb fat-soluble molecules and poorly absorbs water and salts; and, since cell membranes have lipid bilayers, it seems likely that lipid-soluble molecules are able to penetrate the skin. However, it has been found that most vegetable oils (including any essential oils in the blend) will form a film on the outer layer of dead skin without being absorbed into the bloodstream. In addition, the viscosity or degree of saturation of the vegetable oil is of paramount importance in its ability to be absorbed. Almond or olive oil (monounsaturated compounds) was found to slowly penetrate the top layer of guinea pig abdominal skin, while flaxseed oil, rich in polyunsaturated compounds, was rapidly absorbed. In view of this fact, it is impossible to deny the external emollient properties of fatty vegetable oils, which makes them very suitable for use as a fatty base for essential oils.

What gets through the skin?

Repeatedly seen sensitization reactions indicate that some components of essential oils still penetrate the skin. However, it is almost impossible to find reliable scientific evidence that such absorption occurs in pharmacologically significant amounts (i.e., that the substance was absorbed in an amount sufficient to cause any systemic reaction, such as a diuretic), is almost impossible. Whole oil does not appear to enter the bloodstream through the skin in any way. The main sources cited by us as support for the dermal absorption thesis give rise to serious uncertainty on several points.

It appears that some components, such as ?-pinene and camphene, are absorbed in significant amounts, as confirmed by an experiment in which pine oil was added to hot bath water (a combination of heat and humidity), while inhaling oil molecules through the nose was prevented using a nose clip. Within 24 hours of application, both chemicals were observed to be excreted from the subject's body via the urine.(2). On the other hand, however, this experiment in a hot bath cannot be equated with the usual use of essential oils in a massage.

Benzoic acid (benzoin) is widely known to be easily absorbed into the skin and is often used to study the variability of absorption across the body surface. It was found that the surface of the inner side of the forearm and back had the best suction ability. Benzyl acetate (jasmine) is excreted in the urine within 24 hours of undiluted oil application. Both natural jasmine absolute and synthetic jasmine fragrance oil elicited a skin irritation reaction when tested. Both benzyl benzoate (ylang-ylang) and benzyl alcohol (constituting up to 30% of Balsam of Peru, Myroxylon Pereirae) were absorbed within 24 hours. Also absorbed are cinnamon alcohol (cinnamon leaves and benzoin) and cinnamic acid (cinnamon bark), which are potent sensitizing components, and safrole (sassafras, Sassafras albium), which is a carcinogen. Cinnamaldehyde (cassia, Cinnamomum, and cinnamon bark) is well absorbed when applied undiluted, but such use is categorically not recommended due to the pronounced property of this substance to cause a sensitization reaction. Methyl salicylate (hornbeam birch, betula grossa, and wintergren, Gaultheria procumbens) is also easily absorbed, especially in the presence of water. Perhaps it is the ease of absorption of the above chemicals into the body that explains their pronounced effect as skin irritants and sensitizing components. It must be taken into account, however, that only a few molecules of the substance are sufficient to "start" the sensitization reaction.

Many studies on the permeability of essential oils through the skin have used isolated, concentrated synthetic fragrances in the form of closed compresses as the prototype for natural essential oils,(3) which can hardly be compared in effect to whole essential oil. Of the dermal absorption studies we found, none included the use of a mask to prevent volatile molecules of a substance from entering the bloodstream via inhalation through the lungs. The exception was the aforementioned pine oil bath study, which used a nose clip. The study materials, however, do not mention how the subject continued to breathe, since the oxygen apparatus was not mentioned in the experimental methodology.

The results of some dermatological tests may not be applicable to humans, since most of these tests, unfortunately, were carried out on animals. Animal skin is much more absorbent than human skin.(3) Results in vitro studies on the effects of the aforementioned isolated chemicals are also not reliable compared to the action of whole oil, and with their action under conditions in vivo. However, care must be taken when using oils containing significant concentrations of such substances.

In vitro Studies in human skin (skin of the breast and foreskin) and in animal skin have shown that benzyl acetate is rapidly absorbed but forms a reservoir in the top layer of dead skin cells (4). This fact indicates that a significant portion of the essential oil applied to the skin may disappear through evaporation rather than absorption. Ethyl alcohol, an essential ingredient in perfume, enhances skin absorption, and recent studies confirm that 75% of any fragrance is absorbed by the skin when applied in a closed compress (open application to the skin does not lead to this result).

Studies of whole oil (lavender) at a concentration of 2% applied to human skin indicate that only two separate chemicals (linalool and linalyl acetate) enter the bloodstream. The methodology of the study does not indicate the concentrations of these substances found, and it is not known whether the presence of any other chemicals in the bloodstream was studied in principle (5). Moreover, in this case also no breathing apparatus was used in order to prevent the penetration of volatile substances into the lungs through breathing. Thus, the exact answer to the question about the ability of the whole essential oil to penetrate the skin was again not received. Note: Since this article was written, a similar test has been performed, which examined an isolated chemical and a breathing apparatus. The detected volume of the substance that entered the bloodstream was not pharmacologically significant compared to the volume of oil used in aromatherapy massage.

In addition, since the skin is a critical organ for the metabolism of drugs and solvents, essential oils may undergo changes before some of their constituent chemicals can penetrate the skin barrier. Essential oils may undergo molecular transformation by [skin] enzymes (P450). Benzyl acetate (jasmine) is very efficiently broken down by the enzyme esterase.

Increasing the skin's ability to absorb chemicals is possible and can be achieved in several different ways. At the same time, it must be remembered that the increased absorbency of the skin may lead to an increased tendency to irritation and sensitization under the influence of any essential oil. Extreme caution should be exercised when working with individuals who are hypersensitive or prone to allergies and atopy (i.e., people with hay fever, allergic rhinitis, eczema, asthma, allergies to animals and their fur or a family history of such manifestations). In addition, extreme caution should be exercised when handling oils with irritating or sensitizing properties in the presence of the following:

The following factors can increase the absorbency of the skin:

Temperature - the patient's skin (be careful before and after exercise or sauna), the air in the aromatherapist's room, the skin of the aromatherapist's hands, the water in the bath.

Humidity, the presence of water - for some time after a long bath, the skin, usually waterproof, is saturated with water and its throughput increases.

The addition of laundry detergent, soap, or solvents has been found to increase the permeability of the skin.

Damaged or thinned skin is more absorbent, which increases the likelihood of an irritation or sensitization reaction (such as eczema, psoriasis, ulcers).

Isolation of the skin area - covering the skin with a compress enhances absorption, preventing evaporation.

CONCLUSIONS:

The thesis that a whole essential oil, especially in pharmacologically significant amounts, is able to penetrate into the bloodstream still needs to be proven. At the moment, it seems very likely that only certain chemical components of oils have this ability. Thus, the statement "whole essential oil penetrates the skin and enters the bloodstream" is false. The volatile components of essential oils do enter the bloodstream quite rapidly through respiration, provided there is an appreciable concentration of such in the air, as demonstrated by their subsequent presence in the blood and urine. However, the exact concentration of those few chemicals that are able to penetrate the skin (and most of which are irritating and sensitizing) through aromatherapy massage, and what concentration is required in order to cause a systemic pharmacological reaction, is still unknown. Thus, it seems likely that many of the properties attributed to essential oils may be the result of their action via inhalation, or an unreliable extrapolation of their action when taken orally (both oil and plant extract). Conclusions about such properties of oils, therefore, may not be applicable to the amounts of essential oils that enter the body through dermal application. The issue of the AMOUNT of essential oils or their constituents that enter the bloodstream through the skin is of fundamental importance, since most people seem to absorb a much larger amount of oils in food and drinks.

The fact that whole essential oils are most likely not able to penetrate the skin into the bloodstream DOES NOT in any way cancel the beneficial effects of essential oils on the skin and on the mental-emotional sphere (relaxation). Dermal application of essential oils has a beneficial effect on the outer layers of the skin, often prone to various diseases. Anti-inflammatory, antibacterial, and many other known beneficial properties make essential oils highly effective in treating a variety of mild to moderate pain and discomfort. In addition, it is impossible to underestimate the joy and relaxing effect of the use of pleasant aromatic substances.

(one). Extract from "Application of Oil in Prevention of Fatty Acid Deficiency in Pre-term Infants". Lee F. Gibson K. Zimmer K. Food & Chemical Toxicology, Vol. 28 Jan. 1985. pgs. 27-28, & Vol 6, 1990. Demonstrates that topical application of safflower oil does not reduce fatty acid deficiency; no evidence of dermal absorption of the oil was found.

(2). "Percutaneous absorption of Essential oils and Compounds". Rommelt, et al 1974, Kosmet Database.

(3). Bronaugh, et. al, Food & Chemical Toxicology, 28(51), 369-373, 1990. "In vivo percutaneous absorption of fragrance ingredients in rhesus monkeys and humans".

(four). Hotchkiss at. al. Food & Chemical Toxicology. 28 (6), 443-447, 1990. "Percutaneous absorption of benzyl acetate through rat skin in vitro. Validation of an in vitro model against in vivo data"; and Hotchkiss et. al. Food & Chemical Toxicology. 30 (2), 145-153, 1992, "Percutaneous absorption of benzyl acetate through rat skin in vitro. Effect of vehicle and occlusion". In which only 4% was absorbed (Bronaugh. 1990)

(5). Buchbauer, J. G, Jirovetz. Firtzer, Journal of Society of Cosmet/c Chemists, 43;49-54, Jan-Feb 92; "Percutaneous Absorption of Lavender from a Massage Oil". After a 10-minute abdominal massage on an adult male test subject, blood samples taken five minutes apart showed (only) traces of linalyl acetate and linalool; the maximum concentration was found after 20 minutes, and these substances were removed from the body after 90 minutes.

Bibliography

Buchbauer, J.G., Jirovetz, Firtzer, Journal of Society of Cosmetic Chemists 43:49-54, Jan-Feb, 1992.

Hanger, Sylla Sheppard, Lisin, G., Watt, M., Moyler, D., (eds.), The Aromatherapy Practitioner Reference Manual, 1995.

Hotchkiss et al. Food & Chemical Toxicology 28(6), 443-447, 1992 and 30(2). 145-153, 1992.

Bronaugh, et al. 28 (5), 369-373, 1990. Kosmet Database reports from IFSCC (International Federation of the Societies of Cosmetic Chemists), National Societies of Cosmetic Chemists, technical publications from professional associations; Delaport House, Luton, Bedfordshire, UK.

Lee, Gibson, & Zimmer, Food and Chemical Toxicology, (28), 27-28. 1985 & (6), 1990.

Watt, M. Plant Aromatics Data & Reference Manual on Essential Oils and Aromatic Plant Extracts. 1994; and personal communications.

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The mechanism of penetration of cosmetics into the skin

Moreover, the composition of cosmetics includes many additional ingredients: emulsifiers, thickeners, gelling agents, stabilizers and preservatives. Each of them performs its own function that affects the overall effect of the product. In this case, it is extremely important to determine the properties of all components and active elements in order to exclude their incompatibility.

How often do we hear that one or another cosmetic product is rich in active ingredients that perfectly penetrate the skin. But we don’t even think that the main task of such ingredients is not just to pass through the epidermis, but to act on a certain layer of it. This also applies to the surface of the skin, the so-called stratum corneum, into which not all substances need to penetrate. Therefore, in order to determine the effectiveness of the drug, it is necessary to take into account its full composition, and not individual elements.

The essence of the active components is that they must get to a specific place, even if it is the surface of the stratum corneum. Therefore, it is necessary to give credit to the means that deliver them there, in other words, to the carriers, which include liposomes. For example, encapsulated retinol, penetrating into the skin, irritates it less than its free counterpart. Moreover, the composition of cosmetics includes many additional ingredients: emulsifiers, thickeners, gelling agents, stabilizers and preservatives. Each of them performs its own function that affects the overall effect of the product. In this case, it is extremely important to determine the properties of all components and active elements in order to exclude their incompatibility.

There is no doubt that the constituents of cosmetic products penetrate the skin. The problem is how to determine how deep they can or must go in order to have an effect on a certain area of ​​the skin, and / or whether they remain cosmetic, and not medicinal products. An equally important issue is how to preserve the integrity of the active ingredients before they reach their destination. Chemists-cosmetologists have been faced with the question more than once: what percentage of such substances achieve their goal?

The use of tyrosine (melanin) inhibitors against hyperpigmentation is a prime example of how important the concept of substance penetration is in determining the effectiveness of a product. In particular, the active component must overcome the lipid barrier of the stratum corneum of the skin, the cellular structure of the epidermis, penetrate into melanocytes and only then into melanosomes. At the same time, the substance must retain its chemical qualities and integrity in order to cause the desired reaction, which will lead to the suppression of the conversion of tyrosine to melanin. And even this is not a very difficult task. Take, for example, sunscreens, which, on the other hand, need to stay on the surface of the skin in order to do their job.

It follows from this that the effectiveness of a cosmetic product is the action not only of its active components, but also of all other substances that make up its composition. At the same time, each of the ingredients should help ensure that the active substances reach their destination without losing their effectiveness.

To determine the degree of effectiveness of the product, you should answer the following questions:

How do products penetrate?
How important is penetration for a cosmetic product?
- Is the penetration of the active ingredients of a cosmetic product important for the treatment of specific skin types or conditions?

To give a full answer to them, one should take into account why, how and what parameters affect the penetration of cosmetic preparations.

What is product penetration?

Product penetration refers to the movement of substances or chemicals through the skin. The stratum corneum forms a barrier, due to which the skin is considered to be a semi-impermeable membrane. This suggests that microorganisms cannot penetrate through the intact epidermis, unlike various chemicals. The skin selectively provides a molecular passageway. Despite this, a significant amount of chemicals when applied topically in the form of cosmetics or lotions is absorbed by the skin (within 60%). Most agents penetrating the skin must overcome the extracellular lipid matrix, since lipids form an almost continuous barrier in the stratum corneum. Its features depend on age, anatomy and even the season. With dry skin or in the course of certain diseases, the stratum corneum becomes so thin that the active ingredients penetrate much easier and faster.

For many buyers, the effectiveness of a product is determined by the penetration capabilities of its ingredients. In fact, it directly depends on a number of factors, including the quantity and quality of active ingredients in the composition of cosmetics, carrier substances that deliver active ingredients to their target, the volume of the latter necessary for their optimal functioning and achievement of the desired result. The active ingredient is considered effective when it reaches the right place in the right concentration, while its effect on other areas is minimal.

For cosmetics, it is equally important that their ingredients do not penetrate into the dermis, and from there into the blood through the capillary system. Getting the product through the skin into the circulatory system transfers it from the category of cosmetics to medicines.

There are two types of delivery of ingredients - dermal and transepidermal. In the first case, the substance acts in the stratum corneum, living epidermis or dermis. In the second - outside the dermis, often affecting the circulatory system. As a rule, cosmetic products are limited to dermal delivery, while transepidermal delivery is characteristic of drugs. Thus, cosmetics should penetrate the skin, not through it. Therefore, one of the key points in the development of such drugs is to prevent the transepidermal penetration of the components and their active action in a certain layer of the skin.

At the moment, scientists are working on two main tasks. The first is that the active component is guaranteed to reach the right place without losing its properties. The second provides for the creation of a mechanism by which the same component will lose its influence if and when it leaves its zone of action.

However, cosmetic chemists often face the following issues:

– how much substance remains on the skin?
- how much of it goes to a given place?
How much can pass through the skin and reach the circulatory system?
– what is the optimal ratio of the features of a cosmetic product?

It should not be forgotten that determining the effectiveness of a product by its ability to penetrate can be erroneous. For example, skin lightening products must penetrate the epidermis, reaching its basal layer, in order to inhibit the tyrosinase enzyme needed to produce melanin. At the same time, such preparations can only remain on the surface of the stratum corneum, and the brightening effect is achieved through the accumulation of pigment. In both cases, cosmetics are effective, but their penetration capabilities are different.

Take, for example, UV absorbers. They must remain on the surface of the skin to protect it. Once these substances penetrate the skin, they become less effective. At the same time, antioxidants and other chemical compounds with anti-aging properties need to get into the epidermis or even the dermis. Thus, the result of their action directly depends on whether they hit the target or not.

Moisturizers also work differently. Those that have occlusive qualities remain on the surface of the skin. Others need to penetrate into its surface layers in order to retain moisture there. From this it follows that the need for the penetration of cosmetics and its productivity is determined by the functions of its ingredients.

Principles of substance penetration

There are two main channels of penetration - extracellular and intercellular. In the local application of cosmetics, the absorbent organ is the skin, in which many target points of action are isolated. Among them: sebaceous pores, ducts of sweat glands, stratum corneum, living epidermis, dermoepidermal junction.

The rate of penetration of active ingredients depends on the size of the molecules, the carrier, the general condition of the skin. The barrier function of the epidermis largely depends on whether the stratum corneum is damaged or not. Its removal or change as a result of peeling, exfoliation, application of alpha hydroxy acids or a preparation containing retinol (vitamin A), dry skin, dermatological diseases (eczema or psoriasis) contribute to greater penetration of the cosmetic product.

In addition, the passage of the stratum corneum is affected by the size of their molecules and the tendency to metabolic interaction with skin biochemistry, cell receptors. If the penetration rate is low, then the concentration of the product will increase. This is facilitated by the fact that the stratum corneum acts as a reservoir. Thus, the tissues located under it will be under the influence of the active substance for a certain time. Due to this, the stratum corneum is both a natural skin barrier and a kind of reservoir that allows you to prolong the effect of a cosmetic product after it is applied to the skin. However, it should be borne in mind that various diseases can change the rate of local absorption. For example, diabetes mellitus changes the structure of the skin, affects its properties. Moreover, the skin on different parts of the body passes chemicals differently. In particular, the face and scalp absorb drugs 5 or even 10 times better.

Methods of penetration of active ingredients

The stratum corneum, with its highly interconnected cells, is a major barrier to product penetration. Another barrier is the basement membrane or dermoepidermal junction. It is not surprising that the question arises, if one of the main functions of the skin is to protect the body from the introduction of foreign substances, then how do the ingredients of cosmetics manage to overcome this barrier. The answer is simple - the skin absorbs them with the help of sebaceous pores, the duct of sweat glands, intercellular channels. In addition, most topical cosmetics do not penetrate the epidermal layer due to one or more of the following reasons:

Molecule size (too big);
retaining or binding a substance to the surface of the skin through other ingredients that make up the product;
evaporation (if the substance is volatile);
adhesion (adhesion) with the cells of the stratum corneum, which disappears in the process of peeling or exfoliation.

How do the components of cosmetics penetrate:

Through epidermal cells or cell cement;
through the formation of a reservoir, when the substance accumulates in the stratum corneum (or subcutaneous fatty tissue), and then is slowly released and absorbed into the tissues;
in the process of natural metabolism in the skin;
pass into the dermis and remain there;
pass into the dermis, are absorbed into the blood circulation system of the capillaries (this resembles the action of drugs, vivid examples are the introduction of nicotine and estrogen).

Of course, it is important to understand why and how active substances penetrate, but one should also take into account the conditions that can influence these processes.

Factors Affecting Product Penetration

The main condition affecting the rate and quality of absorption of the substance by the skin is the healthy state of the stratum corneum. Second is skin hydration. Not surprisingly, the most common method of improving the penetration of cosmetics is occlusion (capture of fluid in the stratum corneum), which prevents the evaporation of moisture from the surface of the skin, which only contributes to its hydration. This is how face masks work. An environment with a relative humidity of 80% also leads to significant hydration of the epidermis. It should be noted that the skin absorbs water well, but cannot always retain it in the right amount. As a result of excessive moisture, the stratum corneum becomes softer (as, for example, with prolonged bathing), its barrier function weakens, which leads to dehydration and increases moisture loss.

One of the main ways of penetration of chemicals into the stratum corneum is through lipid-containing intercellular spaces. Therefore, the lipid composition of this layer of the skin also affects the penetration of active ingredients. Given the oil-to-oil miscibility, chemical ingredients with oil-based carriers will penetrate better than their water-based counterparts. However, lipophilic (oil-based) chemicals are more difficult to penetrate continuously due to the fact that the lower layers of the epidermis have a higher water content than the stratum corneum, therefore they are considered lipophobic. As you know, oil and water practically do not mix. Therefore, the carriers with which the product ingredients are fused for easier application and concentration control also play an important role in determining the rate of penetration.

In some cases, chemical absorption is not limited by the barrier function of the skin, but by the properties of the carrier itself. For example, products in which active substances must remain on the surface of the epidermis (sunscreens and moisturizers) are more effective if they are oil-based. On the other hand, the passage of hydrophilic (water-based) active substances into the intercellular space containing lipids requires either a series of cosmetic manipulations aimed at moisturizing the stratum corneum, or the involvement of liposomes as carriers.

The main difficulties associated with the penetration of active substances are how fast the ingredients move and the depth they reach. Several methods have been developed to control these parameters. They involve the use of special carriers (liposomes), natural encapsulating materials, and other systems. In any case, whatever technique the manufacturer chooses, his main task is to ensure the penetration of active substances to the required area with the maximum possible effect and without side reactions in the form of irritation or skin absorption.

Product testing

There are various test methods to determine the action of the active ingredient in the skin and its location after topical application. Such tests are carried out both in the laboratory and in natural conditions, often using complex computer programs. For laboratory tests, the skin is cultured in glass tubes where the cells multiply about 20 or more times. Often, skin samples are used from patients who have undergone plastic or any other surgery, during which a piece of the epidermis was removed. Such tests have great advantages in terms of time, cost and ethical considerations - especially if they can be toxic.

Under natural conditions, cosmetics are tested on animals and humans. The test results differ in more specific data, as close as possible to reality, which is especially valuable when the systemic effect of the product is in doubt, in other words, how the drug can affect the body as a whole. The methods used depend on what scientists are trying to prove. For example, to determine the level of moisturizing and restorative properties of a product for dry skin, experts recruit volunteers who will have to use ordinary soap-containing preparations on the skin for several days without additional moisturizing. After that, the dryness of the epidermis is tested. The researchers then give moisturizing products to one group of subjects and a placebo to another. At certain intervals, the level of skin hydration among all groups is checked to determine the rate of saturation of the skin with moisture.

During the testing of sunscreen preparations, the main task of the tests is to preserve the active substances on the surface of the stratum corneum, ensuring their maximum effectiveness and preventing toxic side effects. In this case, scraping with adhesive tape, blood and urine tests are used. As a result of such tests, some substances were found in blood plasma and urine. The exception was mineral-based sunscreens.

When testing products that should remain on the surface of the skin or in the stratum corneum, scientists first apply the drug, and then take skin samples with adhesive tape or with a scratch test. The rate of product penetration and cellular changes at different levels of penetration are then studied using computer models. By the same principle, the systemic effect of products is studied. Computer programs allow not only to understand how deeply the agent penetrates, but also what changes in the cellular structure it can cause. Particular attention is paid to the consequences of penetration of the product into the skin, blood, urine and other biological fluids are examined. Some substances may be present in the body in such low concentrations that they can only be detected with very sensitive equipment.

Given the functions of the skin, products (in particular, specific components that make up their composition) under appropriate conditions penetrate through absorption, absorption. But not always the penetration of the product determines its effectiveness. In some cases, it may be undesirable or even harmful.

Advances in cosmetic chemistry have made it possible to better understand

Modern technologies make it possible to achieve such a level of craftsmanship in light industry that things made of artificial leather are almost impossible to distinguish from natural materials. However, the quality of synthetic raw materials still differs significantly from the original, not to mention the price. Having bought faux leather boots, you should not be surprised if they do not survive until the end of the season. The same applies to bags, straps, jackets, etc. Unscrupulous sellers, having high-quality artificial leather products in their hands, often pass them off as natural, thereby increasing the cost by several times. To avoid misunderstandings, disappointments and unnecessary purchases, you should learn to distinguish between genuine leather and fake, as well as know the external signs of different types of leather.

Genuine leather: appearance and types of dressing

Genuine leather is a material obtained by processing the skins of animals - sheep, goats, cows, pigs. It is valued in the light industry for its high technological characteristics: environmental friendliness, softness, elasticity, ability to keep its shape, attractive appearance and unique aroma. You can determine the type of skin using a measure, traces of hair follicles on the surface of the skin, forming a special intricate pattern. It remains after hair removal in place of hair bags. The porous surface of natural leather is due to the interweaving of collagen fibers, a natural protein that forms the basis of the skin. Intertwined with each other, the fibers form bundles and voids, causing uneven skin relief. Depending on the age of the animal and on the method of dressing, the skin has different thickness, elasticity and other characteristics. One of the differences between genuine leather and artificial leather is tanning - the transformation of an ordinary skin into leather. There are the following types of tanning:

1. Chrome tanning is carried out using various chromium compounds. The skin is very strong, breathable, elastic. Among the disadvantages are excessive hygroscopicity, moisture permeability, inability to keep the shape and embossing. Chromed leather has a gray tint.
2. Aluminum tanning is only applied to kid leather, i.e. skin of a young sheep or goat. The skin is incredibly soft, delicate and thin. Gloves are mainly made from it. It is not suitable for the production of shoes, because it absorbs water, losing tannins, and when dried, it becomes rough and covered with cracks.
3. Fat tanning with the fats of marine animals (seals, whales, fur seals) or fish is used to obtain suede - very durable waterproof leather with a fleecy surface. Suede has a natural yellow or beige hue. It stretches well and does not absorb water.
4. Combined tanning combines the use of mineral and artificial tanning agents, resulting in a reduction in the cost of the product. With this type of dressing, raw materials are obtained for the manufacture of straps, wallets, purses, purses, etc.
5. Chromozirconosintane and chromotitanozirconium tanning consists in the use of titanium and zirconium tanning agents to obtain thin light leather with high technical characteristics. However, the final product is not only beautiful, but also expensive.

Artificial leather: appearance and types of dressing

Artificial leather is obtained from composite polymer materials, has a fibrous base or does without it. The main difference from the natural analogue is the absence of a porous structure. Depending on the polymer used, artificial leather can be of the following types:

• based on polyurethane
• based on PVC
• based on polyacetate
• based on nitrocellulose
• based on thermoplastic elastomers
• rubber based

Artificial leather is superior to natural material in some ways. It is produced not in uneven pieces, but in rolls of the correct geometric shape without flaws, so it is easier to work with synthetic materials. Thanks to various additives, leatherette is wear-resistant, does not absorb moisture, and is resistant to temperature extremes. However, non-natural material is significantly inferior in price to its natural counterpart, so it is worth mastering the skills of discrimination so as not to acquire a substitute, even if it is of high quality.

What are the ways to distinguish genuine leather from artificial

There are many ways to determine the authenticity of the skin. These include the following:

1. The inscriptions on the labels will help in determining the origin of the material: Genuine Leather in English, Echtes Leder in German, Cuir in French means "genuine leather".
2. The folded edges of the product will also indicate the naturalness of the material: the seam or hem in genuine leather will be thick and convex, in artificial material it is usually soldered into the thing.
3. Look at the pores on the surface of the skin. For natural raw materials, they are located in a chaotic manner, and for artificial raw materials, they are at the same distance from each other.
4. Run your fingers over the surface of the product. Natural material always seems rougher and tougher, while artificial leather is softer and smoother.
5. Press on the toe of the shoe: if wrinkles appeared on it for a while, but they quickly disappeared, and the surface became absolutely smooth, you have genuine leather boots. If the dent retained its shape, and the place of pressing was covered with small cracks, this indicates an unnatural origin of the material. In principle, such shoes can be attributed to the season, but after a few weeks of wearing, they will have a very shabby look. Artificial leather does not withstand loads, paint quickly peels off it, it fades and cracks.
6. You can check the product with the warmth of your hands. Touch the bag (wallet, gloves, boots) with your palm and hold it for a few seconds. Natural material will heat up, and there will be no perspiration left on it. Artificial leather will begin to give off coolness, and a wet spot will become noticeable along the contour of the palm.
7. Leatherette has a special "chemical" smell, and genuine leather exudes a rather pleasant natural aroma of the processed material.
8. A cut of the skin will help to recognize the original from the substitute. For natural raw materials, it does not have layers, while for synthetic material, the base, interlayer and top layer will be visible.
9. Genuine leather does not absorb water. Drop water on the product: if a drop rolls off the surface, you have 100% leather in front of you, and if water is absorbed, there is a high probability of artificial raw materials.

To be sure of the origin of the skin, rely on time-tested methods: carefully examine the seams, peer into the pattern of the skin, feel its structure with your fingers. Natural shoes are much more reliable than artificial ones, and kid gloves will not be demolished for decades. Make no mistake with the purchase by following the advice for checking the origin of raw materials.

Video: how to distinguish genuine leather from leatherette