Ingredient index

Retinal

A retinoid one conversion step from retinoic acid, so it works faster than retinol at similar tolerability.

What it can share a night with

With	Verdict	Why
Glycolic acid	Alternate nights	Both accelerate turnover. Stacked on one night they routinely produce the stinging and tightness that gets mistaken for sensitive skin. Alternate nights instead.
Niacinamide	Layer freely	Niacinamide supports barrier lipids, which is precisely what a retinoid depletes early on. Layering them the same night is well tolerated.