Overview of Chemical Exfoliation
Chemical exfoliation uses acids or enzymes to dissolve the bonds between dead skin cells in the stratum corneum, accelerating cell turnover. Unlike mechanical exfoliation (scrubs, brushes), chemical exfoliants penetrate into the skin and can affect living cell layers depending on their concentration and pH. Esthetics board exams test the source, skin type application, and contraindications for each type.
Alpha Hydroxy Acids (AHAs)
AHAs are water-soluble acids derived from natural food sources. They work on the surface of the skin, dissolving the bonds between dead cells in the stratum corneum. They are best for dry, dehydrated, mature, or sun-damaged skin because they improve moisture retention.
| AHA | Natural Source | Key Property |
|---|---|---|
| Glycolic acid | Sugar cane | Smallest molecule of all AHAs; deepest penetration; most studied; most potent |
| Lactic acid | Milk (fermented) | Larger molecule than glycolic; gentler; also a humectant (attracts moisture); good for sensitive skin |
| Malic acid | Apples | Milder; often combined with other AHAs |
| Citric acid | Citrus fruits | Antioxidant properties; helps even skin tone; also used as a pH adjuster |
| Tartaric acid | Grapes (wine) | Antioxidant; brightening; typically used in combination formulas |
Beta Hydroxy Acids (BHAs)
BHAs are oil-soluble, which allows them to penetrate into the pore lining (sebaceous follicle). Salicylic acid is the only BHA used in esthetics practice.
- Salicylic acid: Derived from willow bark (also synthesized). Oil-soluble; penetrates the pore and dissolves sebum and debris inside the follicle. Anti-inflammatory and antibacterial properties make it the top choice for oily, acneic, and congested skin types.
Enzyme Peels
Enzyme peels use proteolytic enzymes (proteins that digest other proteins) to break down keratin in dead skin cells. They are the gentlest form of chemical exfoliation and are appropriate for sensitive, reactive, or rosacea-prone skin.
- Papain: Derived from papaya. The most commonly used enzyme in esthetics.
- Bromelain: Derived from pineapple. Similar action to papain; slightly less common.
Enzyme peels do not require neutralization and do not penetrate below the stratum corneum. They are self-limiting: once all the dead cell protein is dissolved, the enzyme stops working.
Concentration Guidelines
Estheticians work within scope-of-practice concentration limits that vary by state. As a general rule:
- Esthetics scope: glycolic acid up to 30% (some states allow up to 20% at certain pH); lactic up to 30%; salicylic up to 2% (FDA OTC limit for leave-on products; professional use varies by state)
- Medical/physician scope: higher concentrations (glycolic 50 to 70%, TCA peels, phenol peels) are outside esthetics practice in most states
Contraindications for Chemical Exfoliation
- Active acne lesions with pustules or open wounds (exacerbates infection)
- Retin-A (tretinoin) or retinoid users (skin is already sensitized; risk of over-exfoliation and burns)
- Recent waxing or depilatory use in the treatment area (barrier is compromised)
- Sunburned or windburned skin
- Rosacea (especially for higher concentrations)
- Aspirin allergy (for salicylic acid, which is chemically related)
- Pregnant clients (some chemical exfoliants are not recommended during pregnancy)