My skincare routine, in the right order

1. Cleanse

A gentle cleanser removes oil and what's left from the night.

2. Toner

A gentle toner. To be honest, there's no evidence a toner adds much. I let it sink in before the vitamin C goes on.

3. Vitamin C

An antioxidant under your sunscreen. In a study, 5% vitamin C cream gave visibly smoother skin than placebo after 6 months.

4. Azelaic acid

For a more even tone: it makes redness and spots less visible. In a small study, a serum with 10% azelaic acid (together with retinal) gave 18% less redness than the same formula without it. Cosmetic serums usually contain 10%. Higher strengths are prescription-only.

How I add it. From week 3 of tretinoin, every other morning at first. If it stings together with vitamin C, I alternate them by morning. Never on the same evening as tretinoin.

Study run by the manufacturer

5. Moisturiser

Keeps your skin hydrated and supports your skin barrier.

6. Sunscreen

The step with the strongest evidence, and extra important with tretinoin. In an Australian study of 903 people, daily use gave 24% less visible skin ageing after 4.5 years than occasional use. Use over half a teaspoon for face, neck and ears.

Dutch RIVM: SPF 30 or higher from UV index 3, reapply every 2 hours

Tretinoin evening

I use tretinoin, a prescription medicine, prescribed by a doctor. The key point: apply it to completely dry skin. Damp skin gives more irritation, so hyaluronic acid doesn't go on right before it on this evening. If it stings, a thin layer of moisturiser can go underneath first.

1. Cleansing oil
2. Gentle cleanser, pat dry
3. Wait until your skin is fully dry
4. Tretinoin, pea-sized amount
5. Moisturiser

Only with a doctor. Tretinoin is prescription-only and only for use after a doctor's assessment. Not during pregnancy or when trying to conceive. In the first weeks your skin can get dry, red or flaky. That usually settles within about 4 weeks. Use SPF 30+ every day, because your skin becomes more sensitive to the sun.

Recovery evening

On evenings without tretinoin I give my skin rest and moisture. Here hyaluronic acid does go on damp skin. In a study, niacinamide (5%) reduced the look of fine lines, spots and redness after 12 weeks.

1. Cleansing oil
2. Gentle cleanser
3. Toner
4. Hyaluronic acid on damp skin
5. Niacinamide
6. Moisturiser

Study run by the manufacturer

Exfoliation evening

Once a week, and only once your skin is used to tretinoin. Acids make your skin more sensitive to the sun: in a study, 10% glycolic acid led to more UV damage after 4 weeks, gone within a week of stopping.

1. Cleansing oil
2. Gentle cleanser
3. Acid toner (exfoliant)
4. Hyaluronic acid on damp skin
5. Niacinamide
6. Moisturiser

Careful. Never on the same evening as tretinoin, and not in the first month.

How to build up

Start slowly. If your skin gets red or flaky, skip a tretinoin evening.

1. Weeks 1 and 2: tretinoin on 2 evenings (Monday and Thursday). The rest are recovery evenings.
2. Weeks 3 and 4: tretinoin on 3 evenings (Monday, Wednesday, Friday), and azelaic acid every other morning.
3. From month 2: as in the week below, with one exfoliation evening on Saturday.

My week

Tap a day to see my morning and evening routine. 'Skin cycling', by the way, hasn't been tested in trials. It comes down to the same two principles: not a retinoid every evening, and acids kept apart from your retinoid.