Retinol

Retinol is a vitamin A derivative that skin converts into retinoic acid, the form that binds to retinoid receptors in the epidermis and dermis.

How it works

Retinol is not active in the form it is applied. Skin enzymes convert it in two steps, first to retinaldehyde and then to retinoic acid. Because that conversion is gradual and limited by enzyme availability, retinol acts more slowly than prescription retinoic acid, and is generally better tolerated, while engaging the same receptor pathway.

What the receptors influence

Once bound, retinoic acid receptors alter gene expression in keratinocytes and dermal fibroblasts. Research associates this with changes to the rate of epidermal cell turnover, the organisation of the stratum corneum, and fibroblast activity in the dermis.

Retinisation

Skin usually passes through an adjustment period when retinol is first introduced, commonly two to four weeks. Dryness, flaking and mild irritation during this window are expected rather than a sign of a reaction. Starting at two to three nights per week and building up gradually reduces the severity of that adjustment.

Light sensitivity

Retinol degrades on exposure to UV, which is why it is formulated for evening use and packaged to limit light exposure. Skin using retinol is also more sensitive to UV, so daily broad-spectrum SPF is needed alongside it.

Pregnancy and breastfeeding

Topical retinol is conventionally avoided during pregnancy. Systemic absorption from topical application is low, but oral retinoids are established teratogens and the standard precaution extends to topical forms. Guidance during breastfeeding is less settled and should be discussed with your doctor.