Retinoid + vitamin C

Be a bit careful. Both are potent actives - together in one session they can irritate, though many people do tolerate the combo.

There's a reason the classic split exists: vitamin C in the morning (antioxidant protection under your SPF) and retinoid at night (repair while you sleep). It's not a rule made up by brands; it just works with how skin and these ingredients behave.

If you're sensitive, new to either, or layering strong versions of both, split them and patch-test. If your skin is seasoned and calm, some overlap is fine.

One myth to retire: vitamin C and niacinamide are fine together - the old 'they cancel out' claim doesn't hold in modern formulas.