Retinoids, and why most people give up in week three

Retinoid dermatitis is not an allergy and not a sign that the product is wrong for you. Retinoids accelerate the turnover of the epidermis, and for several weeks the barrier runs behind: water loss through the skin rises, the face feels tight, and there is flaking — particularly around the nose, the corners of the mouth and the eyelids. Redness, and stinging when other products go on, are both common. Some people, especially those with acne, get a wave of spots as subclinical comedones are pushed through.

It settles. In most people the worst of it falls between day ten and day thirty, and by eight to twelve weeks the skin tolerates nightly use. What distinguishes ordinary adjustment from a real problem is the pattern: irritation is diffuse, dose-dependent and improves when you use the product less often. A sharply demarcated, intensely itchy or blistering eruption is not adjustment and should be looked at.

• Two nights a week for two weeks.
• Then alternate nights for two to four weeks.
• Then nightly, if the skin is comfortable. Plenty of people do very well at four nights a week indefinitely, and that is not a failure.

A pea-sized amount for the entire face. More does not work faster; it only irritates. Apply to dry skin, because applying to damp skin increases penetration and, at this stage, increases irritation with it. If you are sensitive, put moisturiser on first and the retinoid on top for the first month. Keep it off the eyelids and out of the deep nasolabial creases at the start, where product pools.

Stop exfoliating acids, scrubs and cleansing brushes entirely for the first six weeks. Do not layer benzoyl peroxide and tretinoin in the same application. Vitamin C in the morning is fine — the elaborate separation schedules circulating online are mostly unnecessary — but if the skin is stinging, simplify everything until it stops.

Stop retinoids five to seven days before waxing, a peel or a laser treatment, and do not restart until the skin has settled and the clinic has said so. A thinned stratum corneum plus wax removes skin.

Acne: an initial worsening in weeks two to six, meaningful improvement at eight to twelve weeks. Texture and tone: about twelve weeks. Pigmentation: three to six months, and only alongside sunscreen. Fine lines: six to twelve months of consistent use, and the effect is real but modest — a softening, not an erasure.

Nothing about a retinoid is fast. Its advantage is that it keeps working for as long as it is used, which is a rare property in this category.

Not in pregnancy or while trying to conceive, and it is generally avoided while breastfeeding. Not during an active rosacea or eczema flare. Not on a barrier that is already compromised — if the skin stings when water touches it, this month's answer is a cleanser, a moisturiser and a sunscreen and nothing else. Not the week before a wedding.

• Too much product, too often, too soon, on the theory that the discomfort is the point. It is not. The peeling is a side effect, not the mechanism.
• Stacking a retinoid with acids, a scrub and a cleansing device, and then blaming the retinoid.
• Stopping in week three and restarting from zero two months later, repeatedly, so the adjustment period never ends.
• Judging it at six weeks. Take a photograph in the same light on the day you start, and do not look at it again until week twelve.

One more thing worth saying plainly: a retinoid does not thin the skin. The idea comes from the thinning of the stratum corneum in the first weeks, which is the dead outer layer. The living epidermis and the dermis both thicken with long-term use, and that is the entire point of the molecule.

If a retinoid is genuinely intolerable after a careful, slow introduction, that is worth saying rather than enduring. Azelaic acid is an underrated alternative, adapalene is often better tolerated than retinol at equivalent effect, and there is no prize for persisting with a product that keeps your barrier broken.