The word "peel" literally means "remove the outer layer", or "refine". In effect, this is a process of exfoliating horned cells to improve the visual appearance and the overall condition of skin.
As a rule, organic acids are the active components of chemical peel.
Types of Chemical Peel According to Affection Depth:
- Superficial peel is effective in the range of several horned epidermis layers. It is the most sparing kind of chemical peel. After the procedure, patients can follow their usual lifestyles. Generally, it is recommended for young problem-prone skin. The effect is not lasting and it is advised to repeat the procedures.
- Medium-depth peel affects the whole horny layer of epidermis up to basilemma. After these procedures, patients need to stay at home for a week because of hyperemia and small- or large-flaked desquamation. This peel is performed to solve particular problems and to fight the age-related skin changes. The effect is long-lasting, and it is recommended to repeat the procedures only in a year.
- Deep chemical peel consists in epidermis rejection with affecting basilemma. This procedure is fairly responsible and performed under anesthesia because it presents a chemical face burn with the following epidermis regeneration. It is directed at the removal of deep wrinkles and scars and is performed at hospital. The effect is rather long-lasting (up to several years), but the procedure can be carried out only once. The rehabilitation period lasts for about 5 months.
Principal Purposes of Chemical Peel
1. Exfoliation (sloughing off) of horned epidermis which results in proliferation (generation) of basal layer cells. This means renewal of the whole skin cover.
2. Removal of skin imperfections and problem solving as a result of exfoliation and particular properties of acids.
3. Activation of protective and regenerating skin functions due to the stress effect of acids.
What Is Chemical Peel Needed for?
Often, chemical peel is chosen to correct cosmetic skin defects of face and other body parts. Consequently, patients are offered:
- Improvement of skin's visual appearance: skin becomes smoother, tenderer, with an even complexion;
- Disappearance of pigment spots, post acne, scars and stretch marks;
- Normalized pH and secretion of sebaceous glands;
- Rejuvenation of face skin due to smoothing of wrinkles, increased skin firmness and plasticity thanks to improved synthesis of collagen;
- Good mood and boost of self-esteem.
Indications for Chemical Peel:
1. Problem-prone skin (post acne, blackheads, comedones);
2. Hyper pigmentation;
3. Low-toned, not elastic, loose skin;
4. Age-related skin changes;
5. Photo aging (skin affected by excessive UV radiation);
6. Scars and ingrown hairs;
7. Oily skin with enlarged pores;
8. Thickening of the horny layer which results in skin roughness;
9. Dull complexion;
10. As a preparatory stage before deeper and more serious cosmetological procedures.
Indications for Chemical Peel Depending on Age:
1. Young age (14+ years) as prescribed by doctor according to indications;
2. 25-30 years in case of acne, post acne, hyper pigmentation, photo aging, as preventive treatment of skin aging;
3. 35 years and mature age to prevent and treat cosmetic defects of skin or to prepare for other cosmetological procedures.
Contraindications for Chemical Peel:
Absolute Contraindications for Chemical Peel:
1. Any chronic diseases in their aggravation stage;
2. Cold-related diseases;
3. Pregnancy and breast-feeding;
4. Predisposition towards hypertrophic or keloid scars;
5. Necessity for radiotherapy;
6. Fresh suntan;
7. Recent (performed less than 8 weeks ago) traumatic procedures (deep cleansing, mesotherapy, laser resurfacing);
8. Mental illnesses;
9. Separate peel component idiosyncrasy;
10. Intake of immunosuppressants, retinoids, photosensitizing medications;
11. Pronounced couperosis;
12. Oncology diseases;
13. IV–VI skin photo types according to Fitzpatrick scale;
14. Skin diseases (eczema, allergic dermatosis, atopic dermatitis, psoriasis, etc.) in their aggravation stage;
15. Infectious skin diseases (viral, bacterial, fungal);
16. Damage of skin cover, traumas in the peel application area;
17. Slow dermal wound healing;
18. Diabetes and hypertensive disease.
Relative Contraindications for Chemical Peel:
1. Multiple nevi;
3. Hyper sensitivity of skin;
4. Age under 18 years;
Mechanism of Acid Peel Action:
1. Damage of epidermis (chemical burn).
2. In response, skin cells start intense synthesis of inflammation mediators, signaling molecules, enzyme increase factors.
3. Mitotic activity of basal cells is increased (cells actively regenerate).
4. New vessels are created and the generation of fibroblasts is intensified. As a consequence, new collagen, elastin, glycosaminoglycans and enzymes are synthesized.
5. Derma is thickened and tightened; all skin layers are moisturized.
How Is Skin Cover Structured?
Knowledge of skin anatomy and physiology is necessary for understanding the mechanism of any cosmetological procedures.
Skin is not only a human body covering. This is a full-fledged organ with a range of particular functions and complicated structure. The overall skin mass amounts to approximately 5% of body weight. Human skin surface is covered with about 5 million hairs. On the average, every square centimeter of skin contains 100 pores and 200 receptors.
Complete renewal of young skin takes 28 days. With advancing age, this process gets slower every year, and the horny layer thickens and becomes uneven. The thickness of the horny layer can also increase under the influence of ultraviolet rays.
Human skin has regular pH 3.5-5.6. If it is noticeably shifted, skin problems, such as rashes and irritation, may appear. pH up to 3.5 (acidic environment) is typical of dry skin, pH more than 5.6 (alkaline environment) - of oily skin. There can also be mixed-type skin, when skin type differs in separate areas. Thus, it is necessary to know your skin type in order to select correct cosmetic solutions.
Skin structure consists of three principal layers: epidermis (upper skin layer), derma, or skin itself, and subcutaneous fat (hypoderm). Each has its own layers, appendages and elements.
The upper layer of skin - epidermis has the utmost importance in cosmetology. Its structure is multilayered. In epidermis, melanin is produced. This pigment determines skin color and its intensity.
Unlike aqueous solutions, oil-soluble substances freely penetrate epidermis because cell membranes contain numerous fats and these substances "dissolve" in them. Epidermis has no blood vessels and is nourished by diffusion of tissue fluid from the underlying derma layer.
Basilemma is the base of epidermis. It is a blastogenic layer of intensively multiplying cells which substitute the ones dying and sloughing off every day.
Above the basal layer, there is a spinous layer in which cells have spine-like appendages. Right here, in the intercellular space, lymph circulates to ensure nourishment and metabolism in epidermis cells.
Above the spinous layer, granular, clear and horny (uppermost) epidermis layers are arranged sequentially.
Cells of Epidermis:
1. Keratinocytes are cells of spinous, basal and granular layers that move permanently. They are created from splitting blastogenic cells of the basilemma located between epidermis and derma. They mature and shift from lower to upper layers (from spinous to granular layer) while cumulating keratin (a very solid protein).
2. Corneocytes are created in the end of keratinocytes lifespan. They are cells without nucleus and basic organelles, a kind of a “bag” full of keratin. Corneocytes are dead cells, flat scales forming the horny layer. They carry out the barrier function of epidermis.
Corneocytes move further up, come to the skin surface, slough off and are substituted by new ones. Corneocyte renewal takes about three weeks.
Corneocytes are mutually bound by a special substance consisting of a double layer of particular lipids – ceramides. Molecules of ceramides have hydrophilic "heads" (water-retaining fragments) and lipophilic "tails" (oil-retaining fragments).
3. Melanocytes are cells of the basilemma that are located in the malpighian layer of epithelium and generate melanin. This pigment carries out the protective function by guarding the human organism from infrared and partially from ultraviolet radiation. The degree of melanin concentration determines the color of skin. The state of basilemma in some cases determines the formation of pigment spots.
4. Langerhans cells carry out the protective function against foreign bodies and microbes.
5. Merkel cells are tactile cells in the basal layer of epidermis. They are responsible for skin sensitivity. Most Merkel cells are located in the skin of fingertips, nose tip and erotogenic zones.
Under basilemma there is derma, or skin itself. It consists of the papillary and reticular layers. Papillary layer is bound to epidermis. The papillary pattern on palms and feet represents nothing else but dermal papillae that can be seen through epidermis. Lower, there is the reticular layer containing sebaceous and perspiratory glands, hair follicles, nerve endings (skin receptors), as well as collagen and yellow fibers.
Skin elasticity and solidity depend directly on the yellow fibers and the amount of collagen in derma.
Subcutaneous fat layer is located under the reticular layer of derma and carries out the amortization and calefacient functions.
Mechanism of Acid Action on Skin
Chemical peels comprise organic acids. Superficial peel involves fruit acids, medium-depth - trichloracetic (TCA), deep peel - phenol and trichloracetic acid in higher concentration.
When applied on skin, according to its concentration and exposure time, acid dissolves horned cells of upper epidermis layers and sometimes the whole epidermis up to basilemma.
In other words, by applying a peel solution, specialists achieve a controlled chemical burn of face skin. Unlike a traumatic burn, in this case the depth of affection is strictly controlled by the cosmetician to solve those particular problems of the patients that have brought them to a cosmetology clinic.
Fruit and some other acids have an exfoliating effect achieved due to loosened cohesion of corneocytes in the horny layer. In response to intensified flaking, cells of the basal layer start active splitting.
Moreover, acids have a moisturizing effect due to accelerated renewal of epidermis because on the surface of keratinocytes, there is a complex of hygroscopic molecules, or NMF – natural moisturizing factor. This factor is mostly contained in young cells.
Chemical acids have a stimulating effect on skin fibroblasts and therefore promote the synthesis of glycosaminoglycans and collagen.
The stress theory also explains the intensified synthesis of intercellular substance in derma. Protective systems of skin are activated in response to stress. Skin is toned, the reparative regeneration of its cells is amplified, and the synthesis of vital molecules is accelerated.
As a result, epidermis grows thinner and derma thickens. Skin surface becomes more elastic and firm, minor wrinkles get smoothed.
Acids normalize the lipid balance, cleanse the canals of sebaceous glands and therefore decrease skin oiliness and prevent acne and comedones.
Exfoliation of horned epidermis cells results in skin whitening. Moreover, some acids affect the synthesis of melanin and also ensure lightening of skin.
Any chemical peel consists of three stages:
1. Pre-peel treatment. Purpose: skin adaptation to the acid and evening out of the upper layer to ensure better penetration of peel solution. It begins 1-2 weeks before the procedure. Specialists use solutions with low acid concentrations.
2. Peel. Purpose: receiving the desired result depending on the choice of the active acid. It is performed on protocol. The concentration, pH and exposure time are determined by cosmetician.
3. After-peel treatment. Purpose: prevention of complications and fixing the result of peel. Homecare solutions are prescribed by the specialist, and patients have to carry out all the instructions. It is also necessary to use sunscreens with SPF 30 or higher.
Correct pre-peel treatment, peel performed by a qualified specialist and well-selected after-peel treatment decrease the risk of complications significantly. All expected responses and complications are described in detail in the article by O.V. Zabnenkova, Ph.D., senior scientific researcher of the reparative skin process laboratory in I.M. Sechenov First Moscow State Medical University.
Fruit acid peels are extremely popular due to their sparing effect and practical absence of unpleasant sensations during and after the procedure.
Fruit acids are used in superficial peels and are called in this way because fruit are the principal source of these acids. In truth, though, natural concentrations differ a lot from those in peels.
Glycolic, or hydroxy-acetic, acid is used more often than not. Its usage promotes mild smoothing of skin relief and normalized synthesis of melanin and keratin. After glycolic peel, the synthesis of collagen is intensified, and therefore skin becomes firmer and more elastic. Glycolic acid has a pronounced anti-inflammatory and stimulating effect. As a consequence, the patient enjoys a significant rejuvenating effect of the procedure. Significant importance is given to glycolic acid usage in prevention and treatment of molluscum contagiosum.
Apart from glycolic acid, superficial chemical peels may comprise lactic, mandelic, hydroxy-succinic, pyroracemic acids. They all are good at exfoliating the horny layer of epidermis, but every acid has its own specific particularities. For instance, pyroracemic acid is used to treat sensitive and loosened skin because it increases its firmness and elasticity, protects from dehydration and strengthens the barrier function of skin.
Lactic acid, on the contrary, has a delicate soothing effect, regulates the moisture balance and serves as an anti-inflammatory agent. Lactic acid peel is especially popular because it can be performed any time and in any season, without risk of hyper pigmentation in contrast with other peels.
However, fruit acid peels are suitable only for patients of young age, their skin having a higher regeneration potential. Problems of mature skin are solved by means of other chemical peels.
Acids Used in Medium-Depth Peels
Trichloracetic acid (TCA peel) and salicylic acid are used in medium-depth and superficial-medium peels. High concentrations of TCA (40-35%) already belong to the deep peel category, are equivalent to surgical cosmetology and demand special conditions.
Medium-depth peels and corresponding acids are used to solve age-related skin problems, such as stretch marks, post acne scars, superficial hyper pigmentation, wrinkles around eyes, in the areas of forehead, upper and lower lip. The effectiveness of the procedure is comparable to that of skin laser resurfacing.
"Frost" effect is a differential characteristic of TCA peel. The treated area of skin whitens slightly. This is a sign of protein denaturation and formation of a barrier film that prevents further penetration of acid into skin. Time of exposure is determined by cosmetician according to the skin type; on dry, thin and sensitive face skin frost appears literally on the first or second minute of peeling, while on body skin with postnatal marks exposure lasts for approximately 10-15 minutes.
After TCA peel, skin needs particular treatment: moisturizing, protection from ultraviolet, stimulation of skin regeneration processes. Trichloracetic acid peel is performed only in autumn or in winter when sun activity is minimal because the risk of stimulated hyper pigmentation in renewed skin is very high.
Salicylic acid is used in medium-depth peels due to its ability to cause deep and intense flaking. The acid concentration in peel solution can amount to 30%. Usually, though, specialists use a 20-25% salicylic acid solution in isopropyl alcohol.
The acid has a keratolytic, anti-inflammatory, antiseptic, de-oiling effect. Desquamation (rejection, exfoliation) of epithelium begins 24 hours after the procedure and lasts for 5-6 days. Skin becomes tender and smooth, like skin of a baby. It needs photoprotective treatment and moisturizing. Salicylic peel is repeated approximately in 2 weeks; number of procedures is determined individually.
This is a form of deep chemical peel, an aggressive, radical and hazardous procedure. Rather, it is a surgical operation which must be performed under anesthesia.
When phenol affects skin, the whole epidermis is rejected and the papillary layer is revealed. This is painful, and there are the risks of contamination, hyper pigmentation and toxic impact of phenol on kidneys, liver and cardiovascular system. According to its impact on skin, phenol peel is comparable to a third-degree burn.
After this procedure, patients need long-term rehabilitation; skin is regenerated in a couple of weeks, and the whole rehabilitation period may last up to six months. The patient should stay at hospital under medical supervision during and after the procedure.