Retinol Glossary
Plain-language definitions for the terms that make retinoid skincare unnecessarily confusing.
Retinoid
The umbrella family of vitamin A–related compounds that includes retinol, retinal, adapalene, tretinoin and others.
Retinol
A vitamin A derivative widely used in over-the-counter cosmetic skincare.
Retinal
Also called retinaldehyde; a cosmetic retinoid one conversion step closer to retinoic acid than retinol.
Tretinoin
Retinoic acid; a prescription topical retinoid in the United States.
Adapalene
A topical retinoid used to treat acne; some strengths are available without prescription in the U.S.
Encapsulation
A formulation technique intended to protect an ingredient or influence its release; it does not by itself prove potency or gentleness.
Purging
An informal skincare term for temporary breakout changes after starting a turnover-affecting active; not every worsening breakout is a purge.
Buffering
Applying moisturizer before a retinoid to reduce irritation.
Sandwich method
Moisturizer, retinoid, then moisturizer again.
Humectant
An ingredient class used to attract and retain water at the skin surface; hyaluronic acid is a common example.