Layering order: thinnest to thickest, always?

Thinnest to thickest. That single rule covers almost every routine; the exceptions are about irritation, not absorption.

The order

1. Cleanser
2. Toner (watery)
3. Essence
4. Serum or ampoule
5. Moisturiser
6. Sunscreen (morning)
7. Oil or occlusive (night, if needed)

The exceptions

• Actives: put a retinoid on dry skin, before moisturiser, at night.
• Vitamin C: morning, before sunscreen, on dry skin.
• Occlusives: always last, and only if your skin is dry.

How long to wait

Thirty seconds between layers is enough for water-based products. Acids and retinoids need 5-10 minutes so they are not diluted.

The mistake that causes most breakouts

Layering four actives in one evening. Introduce one product at a time, two weeks apart. If something stings, stop - stinging is not "working".

Related: the five-step routine.