Salicylic acid

What it is

Salicylic acid is a beta hydroxy acid first obtained from willow bark and now made synthetically. It is oil-soluble, so it travels into the oily lining of a pore, where it softens keratin, loosens the glue between dead cells and slows the shedding that blocks follicles¹. Higher strengths treat warts, corns, dandruff and scaly conditions such as psoriasis¹.

What the evidence says

Evidence: moderate. A long-established acne ingredient dermatologists recommend for blackheads, whiteheads and mild spots; low-strength trial evidence is thinner than for benzoyl peroxide or retinoids.

The American Academy of Dermatology lists salicylic acid as effective for whiteheads and pimples and notes that any acne treatment needs six to eight weeks before breakouts reduce². Over-the-counter acne products use 0.5 to 2%; the 15 to 30% preparations for warts and peels are a different thing¹. Because it unblocks pores rather than killing bacteria or calming deep inflammation, it suits congested, oily skin and does little for painful cysts. Our oily skin guide covers where it fits.

Willow bark extract, sold as the "natural" version, contains salicin, which the body converts to salicylic acid after swallowing. Its research is almost entirely about oral use for back and joint pain, not skin⁵, and the salicylate in a cosmetic extract is small and variable, so expect it to be gentler and far less predictable than a formulated 1 or 2% product.

How people use it

• Leave-on product, 0.5 to 2%: a thin layer over the whole acne-prone area once daily, building to twice daily if tolerated.
• Cleanser: a wash is gentler because it rinses off, but does less.
• Moisturise and wear sunscreen: freshly exfoliated skin dries out and burns more easily.
• Alternate, do not stack: use it on different nights from retinoids or other acids.

Cautions

• Stinging, dryness and peeling are common at first; cut back to every other day rather than pushing through^{1, 3}.
• Keep it off large areas, dressings and broken skin. It is absorbed, and overuse can cause ringing in the ears, dizziness, nausea or confusion, which need urgent medical attention^{1, 3}.
• If you are allergic to aspirin or other salicylates, ask a pharmacist first^{3, 5}.
• In pregnancy, low-strength topical use for a limited time is generally considered acceptable, but confirm with your midwife or doctor and avoid large areas and peels^{1, 4}.
• Children under two should not use it; children and teenagers with chickenpox or flu should avoid salicylates^{1, 3}.
• Irritation from overuse can leave dark marks in brown and Black skin; gentle, consistent use wins.