Quick Comparison
| Adapalene | Salicylic Acid | |
|---|---|---|
| Typical Concentration | OTC: 0.1% gel, apply pea-sized amount once nightly to clean, dry skin. Prescription: 0.3% gel for more resistant acne. Can be applied to slightly damp skin with less irritation than tretinoin. Results visible at 8-12 weeks. | Concentrations: 0.5-2% for daily use products (cleansers, toners, serums). Up to 30% for professional peels. Start with 0.5-1% every other day and increase. Leave-on products are more effective than wash-off. For body acne (back, chest): 2% is standard. |
| Application | Topical (gel, cream, lotion). More stable than tretinoin — can tolerate some benzoyl peroxide layering (Epiduo combines both). | Topical (cleanser, toner, serum, spot treatment, body wash, peel). Leave-on products provide better efficacy than wash-off. |
| Research Papers | 8 papers | 10 papers |
| Categories |
Mechanism of Action
Adapalene
Adapalene selectively binds RAR-beta and RAR-gamma (minimal RAR-alpha affinity), reducing inflammatory signaling compared to pan-RAR agonists. It normalizes follicular epithelial differentiation and reduces corneocyte cohesion in the pilosebaceous unit, preventing microcomedo formation. Adapalene inhibits AP-1 transcription factor (c-Fos/c-Jun dimerization), suppressing IL-6, TNF-alpha, and neutrophil chemotaxis. It promotes comedolysis by accelerating desquamation of existing comedones. For anti-aging, it stimulates fibroblast collagen I and III via RAR-beta/gamma, with comparable efficacy to tretinoin. Its lipophilic naphthoic acid structure confers superior follicular penetration and light stability.
Salicylic Acid
Salicylic acid (ortho-hydroxybenzoic acid) is a lipophilic beta-hydroxy acid—the ortho hydroxyl enables sebum and follicular lipid solubility, unlike water-soluble AHAs. It penetrates the pilosebaceous unit and induces desmolysis: disruption of desmosomal attachments and corneodesmosomes, accelerating desquamation of pore-clogging debris. Inside the follicle, it dissolves sebum and keratin plugs (comedolysis). Salicylic acid inhibits COX-1 and COX-2, reducing prostaglandin synthesis—the same anti-inflammatory mechanism as aspirin—decreasing erythema and swelling. Bacteriostatic against Cutibacterium acnes through membrane disruption and pH reduction. May reduce sebum production. Small size (138 Da) and lipophilicity enable follicular penetration to depths AHAs cannot reach.
Risks & Safety
Adapalene
Common
Dryness, peeling, redness — generally less than tretinoin. Initial purging for 4-6 weeks.
Serious
Avoid in pregnancy (retinoid class).
Rare
Allergic contact dermatitis, severe peeling.
Salicylic Acid
Common
Dryness, peeling, mild stinging. Over-use can compromise the skin barrier.
Serious
Salicylate sensitivity (rare) — avoid if allergic to aspirin. Not recommended in pregnancy at high concentrations.
Rare
Severe peeling from over-application.
Full Profiles
Adapalene →
A third-generation synthetic retinoid originally developed for acne that has significant anti-aging benefits. Adapalene is more stable than tretinoin (resistant to light and oxygen degradation) and better tolerated because it selectively binds to RAR-beta and RAR-gamma receptors rather than all three subtypes. The 0.1% concentration became available OTC in 2016 (Differin), making it the most accessible prescription-strength retinoid.
Salicylic Acid →
The only beta-hydroxy acid (BHA) used in skincare. Salicylic acid is oil-soluble, meaning it can penetrate into pores and dissolve the sebum and dead skin that cause blackheads and acne. This makes it fundamentally different from AHAs (which only work on the skin surface). It also has direct anti-inflammatory properties, reducing the redness and swelling of acne lesions.