Tr
Tretinoin
TretinoinActive
Prescription-only retinoid. Same mechanism as retinol but acts directly without conversion — stronger and faster.
What it does
Tretinoin is the active form of vitamin A. Because the skin doesn't need to convert it (unlike retinol), it's roughly 20× more potent. Used for acne, photoaging, and pigment irregularities. Available in concentrations from 0.025% to 0.1% (cream, gel, microsphere). Available by prescription in most regions. Initial irritation is more pronounced than retinol; pairing with a moisturizer (sandwich method) helps tolerance.
The evidence, graded
strongOlder tretinoin formulations are partially deactivated by benzoyl peroxide when layered, but newer micro-encapsulated formulations are designed to combine. Some prescriptions intentionally combine them.Martin 1998 · British Journal of Dermatology ↗
strongAll topical retinoids — tretinoin, adapalene, retinol, retinaldehyde, retinyl palmitate, and hydroxypinacolone retinoate — are not recommended during pregnancy. Direct human data exist mainly for the prescription retinoids (tretinoin, adapalene); the caution extends to the others as a precautionary class-effect. Data on inadvertent exposure reassure but aren't strong enough to recommend any retinoid in pregnancy.Kaplan 2015 · British Journal of Dermatology ↗
expert consensusTretinoin is significantly more potent than retinol; combining it with AHAs the same evening raises irritation risk substantially.Mukherjee 2006 · Clinical Interventions in Aging ↗
expert consensusAzelaic acid and retinol generally pair well. Azelaic acid's anti-inflammatory effect can offset retinoid irritation, and the two are commonly stacked for acne and post-inflammatory pigmentation.Sieber 2014 · Skin Pharmacology and Physiology ↗
expert consensusMandelic acid is the gentlest common AHA, but stacking it with a retinoid the same evening still raises irritation risk for sensitive skin.Kornhauser 2010 · Clinical and Cosmetic Investigative Dermatology ↗
expert consensusApplying moisturizer before AND after tretinoin (the 'sandwich method') reduces irritation without significantly reducing efficacy for most users.Mukherjee 2006 · Clinical Interventions in Aging ↗
expert consensusFor cosmetic anti-aging purposes, retinoids are not recommended under 18. Teen skin is already producing high collagen and cell turnover, and retinoid use in young people is reserved for treating conditions like acne — not for prevention of aging.Motamedi 2021 · Journal of Cutaneous Medicine and Surgery ↗
emergingL-ascorbic acid is acidic (pH around 3); applied directly with retinol it can cause irritation and may compromise stability of both. Most users do better with vitamin C in the AM and retinol in the PM.Pinnell 2001 · Dermatologic Surgery ↗
emergingNiacinamide may reduce retinol-induced irritation while complementing its anti-aging benefits.Bissett 2002 · Cutis ↗
Graded per the methodology: strong · moderate · emerging · expert consensus. A weak source on a strong claim gets the weaker label.
Also known as
all-trans retinoic acid, retin-a
Pairs worth knowing
This page is public and indexed on purpose (unlike profiles and drops, which are unlisted) — it’s the citation behind shared ingredient cards, and it should be findable.
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