retinol

How it works, mechanically

Skin cannot use retinol directly. It has to convert it, in two steps, into retinoic acid, which is the form that is actually active. Each conversion step loses material, so a retinol product delivers considerably less active than a prescription retinoid of the same nominal strength. That inefficiency is the whole reason retinol is available without a prescription: it is slower and gentler because most of it never becomes active at all.

• Two conversion steps. Retinol to retinaldehyde to retinoic acid, with losses at each stage.
• Slower than a prescription retinoid. That is the trade being made, and it is a deliberate one.
• Concentration is not comparable across brands. Percentage alone tells you little without knowing the form and the formula around it.

The schedule is the instruction

Starting daily is the commonest mistake and the one that ends most retinol routines within a fortnight. The usual approach is twice a week for the first two to three weeks, then every other night, then daily only if the skin has stayed comfortable throughout. Dryness, flaking and tightness in the first weeks are well documented and are a signal to slow down rather than to push on.

• Begin at twice a week. Increase only after several weeks without irritation.
• Night only. Retinol degrades in light and increases sensitivity to it.
• Daily sunscreen while using it. Photosensitivity is the best established practical consequence of using it at all.
• Do not stack it with acids on the same night. Combining actives is where most avoidable irritation comes from.

Who should ask a doctor first

This part is not a formality. Retinoids as a class carry a pregnancy caution, and while the evidence around low strength topical retinol is different from that around oral or prescription retinoids, standard advice is to avoid it during pregnancy and breastfeeding unless a doctor says otherwise. Anyone using a prescription skin treatment, or managing a diagnosed condition, should also raise it before adding this to a routine.

• Pregnant or breastfeeding. Ask a doctor before using any retinoid, including a cosmetic strength one.
• On prescription skin treatment. Interactions are a matter for whoever wrote the prescription.
• Sensitive or compromised skin. Broken, sunburnt or actively irritated skin is not where to begin.
• Nothing here is medical advice. This is a description of how a cosmetic ingredient is normally used, and a doctor's answer overrides it.

Where it sits on this shelf

Something worth flagging plainly: all twelve of these are body products rather than face products, spread across a bust care line and a booty line. Retinol is far better known as a facial ingredient, so if you have read about it before, that reading was almost certainly about a different application on much thinner skin.

• Nine are bust care. Butters, scrubs and serums sold individually and as sets.
• Three are the booty line. The same three formats under a different name.
• Body skin is not face skin. It is thicker and generally more tolerant, but the schedule and the cautions above still apply.
• Several are also on other shelves. The butters appear on the whipped body butter page and the scrubs on the sugar scrub page.