How to layer actives without wrecking your barrier

Most irritation does not come from a bad product. It comes from three good ones stacked on the same evening.

The order

Apply thinnest to thickest. Water-based serums first, onto skin that is still slightly damp, then a cream, then an oil if you use one. Each layer seals the one beneath it, so reversing the order simply means the serum never reaches the skin.

One new thing at a time

Introduce a single new active and give it four weeks before adding another. If you already use a retinoid or a strong acid, alternate evenings rather than combining them. Your skin is not building tolerance to two things at once.

Signs you have gone too far

Tightness after cleansing, stinging from products that used to be fine, small flakes around the nose. Stop the actives, run a plain cream twice a day for a week, and restart at half the frequency.

A simple week

Monday and Thursday: exfoliant, then cream. Every other evening: serum, then cream. Every morning: serum, cream, SPF. That is the whole thing.