Why does my skin sting when I apply products?

Stinging almost always means a compromised barrier, not that a product is 'working' — healthy skin shouldn't sting from normal application.

A small amount of tingling from a strong active occasionally is one thing, but regular stinging on application means the outermost barrier layer is compromised enough that ingredients are reaching live nerve endings faster than they should. This usually follows a stretch of over-exfoliating, over-cleansing, or layering too many actives — the fix is stepping back to a minimal, barrier-focused routine for a couple of weeks before reintroducing actives slowly.