How it works
Tretinoin binds retinoic acid receptors (RAR-α, β, γ) in keratinocytes, normalizing cellular turnover, reducing comedone formation, and stimulating dermal collagen synthesis.
The evidence
FDA-approved since 1971. Decades of trials support efficacy for acne and photodamage at 0.025–0.1% concentrations. Combined formulations (with niacinamide, azelaic acid) are routinely compounded for tolerability.
Typical dosing
Pea-sized amount applied to clean dry skin at night, 3–7 nights per week depending on tolerance. Start lower concentration (0.025%) for sensitive skin. Daily sunscreen is mandatory.
Side effects
Common
- Dryness
- Peeling
- Initial breakout (purge)
- Photosensitivity
Less common
- Hyperpigmentation in darker skin if used aggressively
Drug interactions
- Other exfoliants (AHA/BHA) — combine with care
- Benzoyl peroxide — may inactivate tretinoin if layered
- Sun exposure — use SPF 30+ daily