What each one does
AHAs (glycolic, lactic, mandelic acid) and BHAs (salicylic acid) loosen the bonds between dead cells at the surface so they shed faster. BHA is oil-soluble, so it also works inside pores.
Retinoids — retinol, retinal (retinaldehyde), and prescription ones like tretinoin and adapalene — work deeper, changing how skin cells turn over. Different route, overlapping result: thinner, more reactive skin while you're getting used to them.
How to use both
Use them on different nights. A common rhythm is a retinoid night, an acid night, then one or two nights with neither — just a cleanser and moisturiser. Let your skin decide how often, not the bottle.
Some people put a gentle acid toner in the morning instead, keeping the retinoid at night. That only works with daily sunscreen, since both leave skin more sensitive to the sun.
If your retinoid was prescribed, ask your prescriber before adding an acid at all.
Signs your barrier is struggling
Skin that stings when you apply a plain moisturiser, looks shiny-tight, flakes, or reacts to products it used to tolerate. Stop both actives, keep the routine to a gentle cleanser, moisturiser and sunscreen until it settles, then reintroduce one at a time.
Common questions
- Can I use retinol and glycolic acid together?
- Not on the same night, for most people. Alternate them — a retinol night, an acid night, and rest nights in between.
- Can I use salicylic acid with retinol?
- Yes, on different nights or at different times of day. A salicylic acid cleanser rinsed off in the morning is usually easier than a leave-on BHA under retinol.
- How long should I wait between an acid and a retinoid?
- Waiting minutes doesn't change much — the irritation comes from using both on the same skin the same night. Separate nights is what makes the difference.
