Antioxidant serum

An antioxidant serum is a lightweight, leave-on product built around antioxidant ingredients — most often vitamin C in one of its many forms, sometimes paired with vitamin E, ferulic acid, niacinamide or plant polyphenols. The serum format is popular here because it carries a relatively high proportion of active in a thin, fast-absorbing base.

Most routines place it in the morning, after cleansing and any watery step, and before moisturiser and sunscreen. The logic is that antioxidants complement UV protection by helping the skin cope with oxidative stress during the day. Formulas built on stable derivatives are equally at home in the evening.

An antioxidant serum is not sunscreen and should not be used in place of one. Pure ascorbic acid formulas can sting, and they oxidise with exposure to light and air — a darkening formula has usually passed its best. Patch test if your skin is sensitive, and introduce one new active at a time.