Retinoids have more evidence behind them than anything else you can buy without a prescription. They also have the highest quit rate, and the two facts are related: people start too strong, peel for two weeks, and stop.
The family, in order of strength
Retinoic acid is the active form, and the only one your skin can use directly. Everything else has to be converted.
- Retinyl esters (retinyl palmitate) need three conversions. Weakest.
- Retinol needs two. The familiar one.
- Retinaldehyde needs one. Noticeably faster than retinol, still well tolerated.
- Adapalene is a synthetic retinoid, sold over the counter in several markets, and genuinely prescription strength.
- Tretinoin is retinoic acid itself. Prescription.
More conversions means gentler and slower. That is the whole trade.
Starting properly
Twice a week, on dry skin, at night. Not every night. Not on damp skin, which increases penetration and is where most of the horror stories come from.
Give it two weeks at that frequency before increasing. Then three nights a week for two more. Most people land at four or five nights and never need more.
If you are irritated, do not stop entirely. Drop back one step and hold there. Stopping and restarting resets the adjustment period, so the stop-start cycle is how people spend six months permanently in week one.
The sandwich, if you need it
Moisturiser, then retinoid, then moisturiser again. It reduces irritation noticeably, and the research suggests it does not meaningfully reduce effectiveness. If the choice is between a sandwich and quitting, sandwich.
What to expect, and when
Texture and tone shift first, usually around eight to twelve weeks. Fine lines take longer, in the range of six months, and the studies that show it run for a year.
Anything promising a difference in a fortnight is describing hydration, not retinoid activity.
Two hard rules
Sunscreen the next morning. Not optional. Retinoids thin the stratum corneum while your skin adjusts, and photosensitivity is real.
Not in pregnancy. Oral retinoids are established teratogens, and while topical absorption is low, the advice everywhere is to avoid them entirely while pregnant or breastfeeding. Azelaic acid and bakuchiol are the usual substitutes, and both are reasonable.