Tretinoin —
The Retinoid That Needs No Converting

Tretinoin, also called all-trans retinoic acid or vitamin A acid, is the active form itself, so the skin does not have to convert it. It works by binding to retinoic acid receptors, which alters how skin cells grow and mature.

For acne, it normalises how the pore lining sheds, so fewer pores block, and helps other acne treatments get in. In sun-aged skin it raises collagen production, tightens the outer layer and slowly evens pigment. Its place in a wider plan is set out in acne treatment and collagen stimulation.

A systematic analysis of randomised studies supports tretinoin for photoageing, with fine wrinkles, roughness and pigment improving over months. Acne guidelines treat topical retinoids as a core treatment, for blackheads and inflamed spots alike. Irritation is the usual reason people stop, and the benefit fades gradually once it ends.

Dryness, peeling and redness are common in the first weeks while the skin adjusts, sometimes called retinisation. The doctor sets the strength, how often and how long, and a gentle cleanser, a ceramide moisturiser and daily sunscreen go with it. Combining it with benzoyl peroxide or an antibiotic is a doctor's decision. For fine lines under the eyes, see under-eye lines.

• Pregnancy, or trying to conceive: not used. Breastfeeding needs a doctor's advice.
• Take care with eczema, rosacea, sunburn or broken skin.
• Pause it in the days around waxing, peels or laser.

It makes skin more sensitive to sun, so daily sunscreen is part of using it.

Tretinoin is prescription-only. Retinoic acid is not permitted in cosmetic products, and the HSA has warned about imported creams found to contain undeclared tretinoin, so buy only through a doctor or a legitimate pharmacy. Before prescribing, a doctor assesses the skin and rules out pregnancy.