What is chemical peeling and classification of acids

Chemical peeling is the application of a chemical agent to the skin that causes controlled destruction of part or all of the epidermis, with or without dermis, leading to exfoliation, removal of superficial lesions, followed by regeneration and renewal of the epidermis and dermis.

Indications for chemical peels:

1) pigment disorders;

2) acne;

3) aesthetic;

4) epidermal growth.

Contraindications:

1) active bacterial, viral, fungal or herpes infection;

2) open wounds;

3) taking medications with photosensitizing properties;

4) preclinical stage of inflammatory dermatoses, such as psoriasis and atopic dermatitis;

5) conflict patients (patients who do not comply with recommendations on limiting insolation or using medications);

6) patients with unrealistic expectations.

7) for medium and deep peels – pathological scarring, keloids, skin atrophy, use of isotretinoin for the last 6 months.

Types of peeling

Superficial peeling acts at the level of the stratum corneum of the epidermis (glycolic, lactic, azelaic, salicylic, phytic, mandelic acids, trichloroacetic (TCA) in a concentration of 1-15%), retinoids, Jessner's solutions. It is the most gentle and popular type of chemical peeling. After this peeling, you can continue your normal lifestyle; side effects are statistically insignificant. There are practically no contraindications, or they are exaggeratedly emphasized in the literature. Later in the article we will focus specifically on superficial chemical peeling, and why will be clear literally immediately.

Important: peelings with AHA acids, especially glycolic acids, are the deepest among superficial ones.

Medium peeling reaches the basal layer of the epidermis and acts at the level of the dermo-epidermal barrier (TCA, phenol, microcrystalline dermabrasion, laser correction, salicylic acid 30%). The number of side effects and contraindications for this type of peeling is quite large.

Deep peeling reaches the level of the reticular dermis (phenolic, for example). The procedure is responsible, medical, and is carried out under anesthesia, since it is nothing more than a chemical burn of the facial skin with subsequent regeneration of the epidermis. It is carried out in a hospital and is aimed at removing deep wrinkles and scars. The effect lasts for a very long time, up to several years, but can be done only once; the rehabilitation period lasts about 5 months. The procedure is traumatic, has many contraindications, restrictions and side effects. In many developed countries, both Western and Eastern, the question has been repeatedly raised at the state level to ban such procedures due to their extreme health hazard. In some countries, deep peeling, such as phenol peeling, is prohibited. We will not consider it in this article.

Classification of acids

AHA acids

AHAs (alpha hydroxy acids, or fruit acids) are a group of natural organic acids found in fruits, sugar cane, sour milk and wine. It has been used by dermatocosmetologists for over 50 years. It is one of the most popular ingredients in cosmetic products. AHAs are able to affect the condition of the skin at the molecular, cellular and tissue level. Safe. When applied to the skin, fruit acids have exfoliating, moisturizing, anti-inflammatory, brightening and antioxidant effects, and also stimulate the synthesis of collagen and glycosaminoglycans in the skin.

The exfoliating effect of these acids is associated with their ability to weaken the adhesion of corneocytes in the lower, young layers of the stratum corneum due to the fact that they affect the activity of certain enzymes involved in the formation of ionic bonds. There is also evidence that exfoliation occurs as a result of increased apoptosis.

The weakening of the adhesion of corneocytes at the level of the granular layer contributes to their faster advancement into the stratum corneum and exfoliation, which is a trigger for the division and differentiation of underlying keratinocytes.

A decrease in corneocyte cohesion also affects the level of skin hydration. NMF (natural skin moisturizing factor) is better developed in young corneocytes, therefore, rapid renewal of the epidermis leads to an increase in the content of functionally active NMF. In addition, hygroscopic AHA molecules are able to bind water and, penetrating deep into the skin, deliver it to the deeper layers.

Despite their exfoliating activity, ANAs have a positive effect on the barrier functions of the skin. This is due to their ability to increase the total amount of ceramides (components of the intercellular lipid layers of the stratum corneum) and modulate their type. This is especially important when there is a deficiency of linoleate-containing ceramides of the first type, as a result of which the permeability of the stratum corneum increases.

ANAs have an anti-inflammatory effect, which is due to their influence on inflammatory mediators and a decrease in the production of hydroxyl radicals. The anti-inflammatory activity of AHA acids depends on their antioxidant activity.

The exfoliating effect of AHAs is attributed to their ability to weaken the cohesion of corneocyte cells in the stratum corneum. In response to increased desquamation, cell division in the basal layer is activated. In the lowest part of the epidermis, adjacent to the dermis, there is the so-called germinal layer, also known as the basal layer. It is here that the birth of new cells occurs, ensuring the processes of regeneration of the epidermis.

Action of AHA acids

Glycolic acid is found in sugar cane and green grapes. Among the AHAs, its molecule is the smallest, so it easily penetrates the epidermal barrier and has the most pronounced effect. It has the ability to reduce hyperpigmentation, reduce hyperkeratinization, smooth out fine wrinkles, improve complexion, normalize the metabolism of epidermal and dermal cells, rejuvenate the skin, restore the structure of collagen and elastin in the dermis, which makes the skin tighten.

Lactic acid is found in sour milk and grapes. It has the most pronounced hydrating (moisturizing) and keratolytic (exfoliating) effect among other AHA acids.

Malic acid is found in many fruits, especially apples and tomatoes. In addition to the exfoliating effect, it stimulates cells, enhancing cellular metabolism.

Tartaric acid, in free or esterified form, is found in ripe grapes and old wine. Has exfoliating, whitening and moisturizing effects. Has a pleasant smell of old wine.

Citric acid is found in citrus fruits. It has the highest molecular weight of all the listed AHA acids. It has a whitening effect on the skin, which is enhanced in the presence of tartaric acid. Has antioxidant and bactericidal properties.

Mandelic acid has all the benefits of AHA, containing a benzene group and becomes lipophilic, which is important for oily, porous skin. At the same time, it causes less irritation due to the large molecule, so it is ideal for sensitive skin.

The structure of mandelic acid is similar to that of broad-spectrum antibiotics, which makes it indispensable in the treatment of patients with skin prone to rashes.

Salicylic acid

Salicylic acid (phenolic aromatic o-hydroxybenzoic acid) exhibits acidic properties, like its analogue phenol. It has a pronounced exfoliating effect due to a decrease in the cohesion of corneocytes as a result of disruption of sulfate, sulfite, sulfide bonds between them.

Being a BHA (beta-hydroxy acid), salicylic acid, stronger than fruit acids, stimulates the renewal of skin cells, providing long-term results, evens out the skin texture due to pronounced large-scale peeling. Salicylic acid reduces hyperkeratosis not only on the surface of the skin, but also in the mouths of the follicles, improving the outflow of sebum and reducing the number of comedones. According to one study, salicylic acid inhibits factors necessary for bacterial replication in tissues.

Thus, peeling based on salicylic acid is indicated in complex therapy for the correction of post-acne, folliculitis, seborrheic dermatitis, oily seborrhea of the face, melasma, rosacea, as well as for mature problematic porous skin.

Azelaic acid

Currently, peeling solutions with azelaic acid, which has bacteriostatic activity against P. acnes and Staphylococcus epidermidis, are actively used. Azelaic acid has anti-inflammatory, sebum-regulating, kerato- and comedonolytic, antibacterial effects without causing microbial resistance (there is no addictive effect). The antibacterial effect is associated with the active transport of azelaic acid into the bacterial cell. Also of positive properties, it is worth noting a decrease in the secretion of free fatty acids on the surface of the skin.

Azelaic acid has a good whitening effect, therefore it is actively used in the treatment of hyperpigmentation, which is due to direct inhibition of tyrosinase. Azelaic acid also has an inhibitory effect on DNA synthesis and cellular respiration of pathological melanocytes.

Trichloroacetic acid

A universal peeling agent is trichloroacetic acid , which has become a classic peeling in cosmetology. The mechanism of action of TCA is based on keratocoagulation and precipitation of proteins of the epidermis and partly the dermis. As a result, a deep inflammatory reaction occurs, causing restructuring of the dermis. It should be taken into account that the concentration of a substance directly correlates with the depth of penetration and, consequently, the depth of destruction.

It must be remembered that, regardless of the concentration, each subsequent application of TCA increases the depth of acid penetration, which is accompanied by the appearance of frost. The nature of frost and erythema are criteria for acid penetration and the degree of damaging effect of peeling.

Currently, 15% TCA is increasingly preferred to achieve significant results with minimal complications.

Phenol

Phenol is one of the peeling solutions, the use of which in practice should be the most balanced. Classic deep phenol (88%) peeling is carried out in a hospital under anesthesia and with constant monitoring of the cardiovascular system, since phenol has a toxic effect.

In the practice of cosmetologists, phenol is actively used in lower concentrations, but with a good cosmetic effect. It is worth remembering that, regardless of the concentration, the toxicity of phenol remains, so its use over large areas is unacceptable and the selection of patients should be more careful.

Phenol peeling causes liquefaction necrosis. As a result, in the post-peeling period all stages of the inflammatory process are observed - inflammation, exudation, proliferation. Thus, a restructuring of the dermis occurs and, as a result, a qualitative improvement in the skin texture.

Retinoic peels

The peculiarity of retinoic peels is the absence of a primary damaging effect on skin structures, which makes it possible to distinguish them into a separate group of peels.

Retinoids include chemicals that interact with specific nuclear receptors (α-, β-, γ-RARs; α-, β-, γ-RXRs) to retinoic acid: tretinoin, isotretinoin, retinaldehyde, retinol palmitate, retinol acetate, b- carotene and adapalene. These components are actively involved in embryogenesis, angiogenesis, and skin homeostasis. After interaction, the receptor-retinoid complex binds to a specific DNA nucleotide sequence, resulting in an increase in the synthesis of the gene transcription regulator protein responsible for the proliferation and differentiation of keratinocytes, sebaceous glands, etc.

Although retinoic peels are superficial peels, their results are comparable to those obtained after medium peels. The mechanism of action of retinoids is associated with the influence on the functioning of cells, changes in the expression of genes responsible for the proliferation and differentiation of keratinocytes. They influence the processes of desquamation, activate the synthesis of collagen and elastin, stimulate angiogenesis and the synthesis of epidermal lipids by the cells of the spinous layer, being one of the most actively used drugs in anti-aging programs for the correction of involutional changes in the skin of various origins.

However, despite their obvious benefits, retinoids cause irritation when applied to the skin, so precursors of retinoic acid are mainly used in cosmetology: retinal, retinol, retinol esters.

This article is part of the special project "PEELINGS"

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