Serum

A serum is a lightweight, fast-absorbing skincare product formulated to deliver a relatively high concentration of active ingredients to the skin. It sits between the lighter hydrating steps and the moisturiser in a routine, and is the stage most often used to target a specific concern such as pigmentation, oiliness, dehydration or the signs of ageing.

Serums are usually made with small molecules in a fluid base so that actives can be delivered efficiently without a heavy, occlusive texture. Common serum actives include niacinamide, hyaluronic acid, vitamin C, retinoids, peptides and exfoliating acids. Because they concentrate on active delivery, most serums contain fewer of the rich emollients and occlusives that a cream provides, which is why they are generally followed by a moisturiser to seal in hydration.

In a routine, a serum is applied to clean skin after any toner or essence and before moisturiser and sunscreen. A few drops are usually enough. Water-based serums are typically layered before oil-based ones. When a serum contains stronger actives such as acids or retinoids, it is wise to introduce it slowly, avoid combining too many potent actives at once, and use daily sun protection.