Retinoids: Mechanism and Evidence
How vitamin-A derivatives work at the cellular level, the strength ladder from retinol to tretinoin, and how to use them without wrecking your barrier.
Retinoids are the most rigorously studied actives in skincare. Understanding how they work makes it obvious why they take time, why they irritate at first, and why sun protection is non-negotiable alongside them.
Mechanism of action
Retinoids bind nuclear retinoic-acid receptors and change gene expression in skin cells. The downstream effects: faster, more orderly keratinocyte turnover (so pores clog less), increased collagen production, and reduced breakdown of existing collagen.
The strength ladder
- Retinyl esters — gentlest, weakest; several conversion steps from active.
- Retinol — the common OTC standard; good evidence at tolerated concentrations.
- Retinaldehyde — one step from active, stronger than retinol, still OTC.
- Tretinoin / tazarotene — prescription retinoic acid; strongest evidence and strongest irritation.
Using them well
- Start low and slow — two or three nights a week, then build up as tolerated.
- Apply to dry skin and pair with a plain moisturiser to buffer irritation.
- Use at night; retinoids are degraded by light and can increase sun sensitivity.
- Always pair with morning .
Frequently asked
Knowledge check
0 / 2 correct1. Why is tretinoin stronger than OTC retinol?
2. Why must retinoids be paired with daily SPF?
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