Salicylic Acid

What it is

Salicylic acid is a beta hydroxy acid (BHA), originally identified in willow bark and meadowsweet but now made synthetically. Unlike the water-loving alpha hydroxy acids it dissolves in oil, so it can get into a pore and loosen the plug of dead cells and sebum. Formulators use it in masks, cleansers and serums aimed at blackheads and spots, and at much lower levels it also works as a preservative. How strongly it acts depends on the pH of the formula as well as the percentage on the label.

What it does well

• Helps clear blackheads and mild to moderate spots

  Salicylic acid peels and leave-on products improve mild to moderate acne in clinical trials, but the 2020 Cochrane review of alpha/beta hydroxy acids for acne rated the certainty of that evidence as low because trials were small and inconsistently designed.

  Moderate evidence

• Does not seem to increase sun sensitivity the way glycolic acid can

  In a controlled human study of solar-simulated radiation (Kornhauser et al., J Dermatol Sci 2009), short-term topical glycolic acid raised the skin's UV sensitivity while an equivalent salicylic acid treatment did not. Daily sunscreen is still sensible with any exfoliant.

  Moderate evidence

• Very little reaches the bloodstream from normal facial use

  After 15 days of 2% salicylic acid applied to the face, measured systemic salicylate exposure was at least five times lower than from a single 81 mg aspirin tablet, and was not increased by acne-prone or photodamaged skin.

  Strong evidence

Worth knowing

• Can sting, dry or flake the skin

  Irritation is dose- and pH-dependent and is more likely with daily use or when it is stacked with retinoids and other acids. It usually settles when frequency is reduced.

  Matters most toPeople with sensitive, dry or already compromised skin, and anyone already using a retinoid or another acid.

• Not permitted in cosmetics for children under 3

  EU law bans salicylic acid in preparations for children under 3 years of age, and products that might be used on them must carry the warning 'Not to be used for children under 3 years of age'. This is a precaution reflecting limited infant data, not evidence of harm in adult use.

  Matters most toParents and carers buying skincare for babies and toddlers.

• High-strength peels are usually avoided in pregnancy

  Absorption from a 2% face product is minimal, so an occasional mask is not a realistic systemic risk; the usual caution applies to professional-strength peels rather than to cosmetic levels.

  Matters most toPeople who are pregnant or breastfeeding, who may prefer to check with a midwife or doctor.

Where the EU stands

Sources (3)

Every link goes to the original: a journal, a PubMed record or an EU document.

1. [1]
   Opinion on salicylic acid (CAS 69-72-7), SCCS/1601/18, Corrigendum of 20-21 June 2019

   SCCS (Scientific Committee on Consumer Safety), European Commission · 2019

   The SCCS considered salicylic acid safe as a preservative at 0.5% and, for other uses, at the concentrations now written into Annex III entry 98; this opinion is the basis cited by Commission Regulation (EU) 2021/850.

2. [2]
   Topical azelaic acid, salicylic acid, nicotinamide, sulphur, zinc and fruit acid (alpha-hydroxy acid) for acne

   Cochrane Database of Systematic Reviews · 2020 · doi:10.1002/14651858.CD011368.pub2

   Salicylic acid and fruit acids showed some benefit for acne, but risk of bias and imprecision meant the evidence was mostly low or very low certainty.

3. [3]
   Percutaneous absorption of salicylic acid after repeated (14-day) in vivo administration to normal, acnegenic or aged human skin

   Journal of Pharmaceutical Sciences · 1997 · doi:10.1021/js960496b

   Systemic salicylate exposure from 2% topical salicylic acid was at least five-fold lower than from 81 mg of oral aspirin, supporting minimal systemic risk in people without broken skin.