The optimal choice of facial chemical exfoliants depends on individual skin type, concerns, and tolerance. Chemical exfoliants fall into three primary categories: alpha-hydroxy acids (AHAs), beta-hydroxy acids (BHAs), and polyhydroxy acids (PHAs). Each group possesses distinct physicochemical properties and dermatological indications. Below is an evidence-based overview of the most efficacious and commonly recommended agents.
1. Alpha-Hydroxy Acids (AHAs)
AHAs are water-soluble and primarily act on the stratum corneum by weakening the cohesion of corneocytes. Ideal for dry, photodamaged, or dull skin.
Common AHAs:
- Glycolic Acid
- Molecular weight: 76 Da (smallest, most penetrative AHA)
- Effects: Enhances collagen synthesis, reduces hyperpigmentation, improves texture
- Evidence: Clinical trials show significant improvement in photoaged skin with concentrations of 8–20% (Stiller et al., 1996)
- Lactic Acid
- Molecular weight: 90 Da (larger, gentler than glycolic)
- Effects: Hydrates while exfoliating, suitable for sensitive or rosacea-prone skin
- Mandelic Acid
- Molecular weight: 152 Da (aromatic AHA with slow penetration)
- Effects: Antibacterial properties, well-tolerated in acne and sensitive skin
- Evidence: Demonstrated efficacy in treating inflammatory acne and melasma (Fabbrocini et al., 2009)
2. Beta-Hydroxy Acids (BHAs)
BHAs are lipid-soluble, allowing them to penetrate sebaceous follicles, making them particularly effective for acne-prone or oily skin.
Primary BHA:
- Salicylic Acid
- Mechanism: Keratolytic, comedolytic, and anti-inflammatory
- Concentration range: 0.5–2% in OTC products
- Evidence: Reduces comedones and inflammatory acne lesions (Kligman & Mills, 1972)
3. Polyhydroxy Acids (PHAs)
PHAs are larger molecules that exfoliate more superficially, with humectant properties and antioxidant effects. Suitable for very sensitive or compromised skin (e.g., eczema, post-procedural).
Common PHAs:
- Gluconolactone
- Lactobionic Acid
Evidence:
- PHAs demonstrate comparable efficacy to AHAs with less irritation and added barrier support (Roure et al., 2009)
Top Formulations and Brands (as of 2024)
| Product | Key Ingredients | Best For | Notes |
|---|---|---|---|
| The Ordinary Glycolic Acid 7% Toning Solution | Glycolic acid | Normal to oily skin | High efficacy at a budget price |
| Paula’s Choice 2% BHA Liquid Exfoliant | Salicylic acid | Acne-prone, oily skin | Gold standard in BHA exfoliation |
| Drunk Elephant T.L.C. Framboos™ Glycolic Night Serum | Glycolic, lactic, salicylic acid | Combination skin | Multifunctional AHA/BHA blend |
| Neostrata Bionic Face Serum | Lactobionic acid | Sensitive, aging skin | High tolerability with antioxidant benefit |
| Allies of Skin Mandelic Pigmentation Corrector Night Serum | Mandelic, lactic, kojic acid | Hyperpigmentation | Synergistic formulation targeting melasma |
Selection Guidelines by Skin Type
| Skin Type | Best Exfoliant Type | Recommended Ingredient |
|---|---|---|
| Dry, photodamaged | AHA | Glycolic or lactic acid |
| Oily, acne-prone | BHA | Salicylic acid |
| Sensitive | PHA or mandelic acid | Gluconolactone, mandelic acid |
| Hyperpigmented | AHA + brighteners | Glycolic + kojic or azelaic acid |
Safety and Usage Considerations
- Frequency: 2–3 times/week for most; daily use requires careful barrier protection.
- Sun protection is mandatory, as exfoliation increases photosensitivity.
- Avoid combining with retinoids or ascorbic acid without dermatological oversight, due to increased irritation risk.
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