A Guide to Chemical Peels

Alpha hydroxy acids are keratolytic agents that work by dissolving bonds that hold dead skin cells together. Alpha hydroxy acids are superficial exfoliants that are commonly compounded from natural ingredients, such as milk, sugars, fruits, or nuts, that have been chemically changed to an acidic pH. Alpha hydroxy acids are effective in remodeling the epidermis and papillary dermis and require a pH of 4.0 or less for histological changes to take place in the skin. Ideally, hydroxy acids thicken the epidermis and improve the skin barrier.

EXFOLIATING THE EPIDERMIS

The stratum corneum is the top layer of the epidermis, which consists of dead keratinized skin cells. Superficial chemical acids will exfoliate the stratum corneum, encourage new cells to regenerate, and improve the skin barrier. In clinical studies, exfoliating the stratum corneum is crucial to skin barrier function and strengthening the epidermis.

DERMIS

At the dermal layer, hydroxy acids stimulate the synthesis of collagen and elastin and restructure the skin by stimulating the liberation of cytokines and growth factors. Common alpha hydroxy acids include:

• acidified amino acid
• benzilic acid
• citric acid
• glycolic acid
• lipohydroxy acid
• lactic acid
• malic acid
• mandelic acid
• tartaric acid

GLYCOLIC ACID

Glycolic acid is one of the most common keratolytic agents used for chemical exfoliation in cosmetic dermatology and works by weakening the binding properties of the lipids that hold the dead skin cells together, thus, encouraging removal of corneocytes from the stratum corneum. Glycolic acid is commonly made from sugar cane and has the smallest molecule of all of the alpha hydroxy acids, which allows deep penetration into the skin.

Benefits of Glycolic Acid

• Antiaging
• Anti-inflammatory
• Antioxidant
• Dissolves cellular lipids
• Encourages cell regeneration
• Lightens hyperpigmentation
• Protects the skin from photodamage
• Stimulates collagen and elastin

Skin Conditions That Can Be Managed With Glycolic Acid

• Acne
• Aging
• Keratosis pilaris
• Photo damage

LACTIC ACID

Lactic acid has great moisture binding properties and is recommended for aging and oily skin conditions, darker skin phototypes, and clients who have sensitive skin conditions. Lactic acid can be derived from fermented milk and has deep keratolytic action. Lactic acid has a larger molecule than glycolic acid, which lessens the risk of irritation and inflammation.

Benefits of Lactic Acid

• Binds moisture
• Prevents evaporation of moisture

Skin Conditions That Can Be Managed With Lactic Acid

• Acne
• Aging
• Dark skin phototypes (III through VI)
• Keratosis pilaris
• Psoriasis
• Rosacea
• Sensitive skin

MALIC ACID

Malic acid is found in the extracts of apples and is a milder form of lactic acid. Malic acid has antifungal properties and can be used on all skin phototypes.

Benefits of Malic Acid

• Binds moisture
• Little irritation

Skin Conditions That Can Be Managed With Malic Acid

• Aging
• Dark skin phototypes (III through VI)
• Rosacea
• Sensitive skin

MANDELIC ACID

Mandelic acid is a large form molecule compared to glycolic acid, which is a smaller molecule, causing less irritation with sensitive or dark skin phototypes. Mandelic acid is made from almonds and is ideal to help improve hyperpigmented conditions, such as melasma and photoaging, and also has the ability to suppress increased tyrosinase and melanogenesis. Studies have shown that when using mandelic acid to treat hyperpigmentation, the results are comparable to, and often better than, using topical hydroquinone. Mandelic acid has potent antibacterial properties and oil absorption ability and is ideal to treat acneic and rosacea skin conditions. With acneic skin conditions, mandelic acid can be combined with salicylic acid for optimal results.

Benefits of Mandelic Acid

• Antibacterial
• Lipophilic
• Inhibits tyrosinase
• Hydrophobic
• Lightens hyperpigmentation
• Prevents melanogenesis

Skin Conditions That Can Be Managed With Mandelic Acid

• Acne
• Dark skin phototypes (III through VI)
• Hyperpigmentation
• Melasma
• Rosacea
• Sun damage

AMINO ACID FILAGGRIN-BASED ANTIOXIDANTS

Amino acid filaggrin-based antioxidants are also known as acidified amino acids. In the skin, amino acids are metabolized from filaggrin, which is a protein that naturally occurs in the epidermis. These amino acids are the primary agents for the skin’s ability to retain moisture and are known as the natural moisturizing factor. In clinical studies, a defect or mutation in the filaggrin gene was shown to be a contributing factor to skin conditions such as atopic eczema.

Benefits of Amino Acid Filaggrin-Based Antioxidants

• Antioxidant
• Humectant
• Increased glycoaminoglycans

Skin Conditions That Can Be Managed With Amino Acid-Based Antioxidants

• Acne
• Aging
• Hyperpigmentation
• Keratosis pilaris
• Oily skin
• Photoaging

CITRIC ACID

Citric acid is found in citrus fruits, such as oranges and lemons, is an antioxidant, and has corrective antiaging benefits. As a bioflavonoid, also known as vitamin P, it is an effective skin brightener and skin lightener. Citric acid minimizes the damaging effects of the sun and can reverse signs of photodamage and solar elastosis. Citric acid can rebuild the skin’s matrix and increase skin firmness and has both preventative antioxidant and corrective antiaging affects. Synergistically, citric acid can be used in combination with other hydroxy acids for optimal benefit and is commonly combined with other alpha and beta hydroxy acids in chemical peel compounds.

Benefits of Citric Acid

• Antibacterial
• Anti-inflammatory
• Antioxidant
• Assists with iron absorption
• Increases circulation
• Skin brightener
• Skin lightener
• Strengthens capillaries

Skin Conditions That Can Be Managed With Citric Acid

• Acne and inflamed lesions
• Aging
• Couperose
• Rosacea
• Sun damage

Chemical exfoliation is ideal to manage skin conditions and offers clinical benefits that manual exfoliating modalities cannot offer. As a professional, knowing the clinical properties of hydroxy acids will help to determine which hydroxy acid is of most benefit when managing skin diseases and disorders. In most cases, alternating hydroxy acids may be necessary to achieve optimal clinical outcomes. The information contained in the article is based on clinical studies and is not considered medical advice nor does it replace a clinical consultation.