Encyclopedia · anti dandruff
Salicylic acid
A scale-loosening ingredient that helps thick flakes and scalp psoriasis plaques and works best paired with an antifungal.
What it is
Salicylic acid (SA) is a beta-hydroxy acid. It is used in dandruff and psoriasis shampoos and in leave-on scalp treatments.
How it works
It dissolves the "glue" between dead skin cells so scale sheds and other actives can reach the skin. It does not treat the underlying yeast or immune cause.
What the studies show
- In a randomized comparison for scalp itch, 3% salicylic acid with 1% hydrocortisone gave the best relief. Salicylic acid alone gave less relief of excoriation than hydrocortisone (Draelos 2005).
- In 154 people, a ciclopirox 1.5% plus SA 3% shampoo and ketoconazole 2% were both effective, and the SA combination cut itch more (Squire 2002).
- In 19 people, piroctone olamine 0.75% plus SA 2% was slightly better than zinc pyrithione 1% (Loden 2000).
- A keratolytic hydrating shampoo showed clinical benefit and good tolerance in mild to moderate psoriasis in a double-blind vehicle-controlled study (industry) (Massiot 2023).
We found no trial isolating salicylic acid alone against placebo for dandruff. The evidence is fairly good as an add-on and weaker alone.
How it's used in studies
Trials used 2-3% in shampoo two to three times a week, as in the studies above.
Side effects and safety
Dryness, stinging and peeling are the usual effects, and it can be drying on coily or coloured hair. Avoid over-using it on already irritated skin. Salicylate absorption is mainly a concern over large areas, in children and in pregnancy, so check with a clinician in those cases.
Bottom line
Reach for salicylic acid when flakes are thick, waxy or plaque-like, then use an antifungal shampoo to keep them away. See scalp psoriasis. Discuss with a doctor.
Studies 4
Draelos ZD et al. An evaluation of topical 3% salicylic acid and 1% hydrocortisone in the maintenance of scalp pruritus. 2005
Tested: 3% salicylic acid, 1% hydrocortisone, and their combination
Result: The combination of 3% salicylic acid and 1% hydrocortisone gave the best relief of scalp itch.
Read the study ↗Squire RA, Goode K. A randomised, single-blind, single-centre clinical trial to evaluate comparative clinical efficacy of shampoos containing ciclopirox olamine (1.5%) and salicylic acid (3%), or ketoconazole (2%, Nizoral) for the treatment of dandruff/seborrhoeic dermatitis. J Dermatolog Treat. 2002
Tested: ciclopirox 1.5% plus salicylic acid 3% shampoo versus ketoconazole 2% shampoo
Result: Both improved dandruff and seborrheic dermatitis; only the ciclopirox combination significantly reduced itch.
Read the study ↗Lodén M et al. The antidandruff efficacy of a shampoo containing piroctone olamine and salicylic acid in comparison to that of a zinc pyrithione shampoo. Int J Cosmet Sci. 2000
Tested: piroctone olamine 0.75% plus salicylic acid 2% versus zinc pyrithione 1% shampoo (double-blind, half-head)
Result: Both strongly cut dandruff; the piroctone olamine combination was slightly better on severity and area.
Read the study ↗Massiot P et al. Clinical benefit and tolerance profile of a keratolytic and hydrating shampoo in subjects with mild to moderate psoriasis. Results from a double-blind, randomized, vehicle-controlled study. 2023
Tested: keratolytic and hydrating shampoo versus vehicle
Result: Reported clinical benefit and good tolerance of a keratolytic hydrating shampoo. Industry study.
Read the study ↗Related
- Piroctone olamineA gentle anti-dandruff ingredient common in European shampoos, with trial results roughly equal to zinc pyrithione but mostly from manufacturers.
- Coal tarOne of the oldest dandruff and psoriasis treatments; it works, but it contains carcinogens, smells, stains and is no longer anyone's first choice.
- Selenium sulfideAn old, inexpensive anti-dandruff active that new trials suggest works about as well as ketoconazole and has been tested across all curl types.
- CiclopiroxAn antifungal shampoo ingredient with randomized-trial support for scalp seborrheic dermatitis and a particular edge on itch, with no good evidence that it grows hair.
- Scalp psoriasisScalp psoriasis is an autoimmune skin condition that needs medical treatment, not just a stronger shampoo, and good options exist from topical steroids to biologics.
- DandruffDandruff is a common, chronic flaking of the scalp driven by yeast, skin oil and your skin's sensitivity, and an antifungal shampoo controls it well as long as you keep using it.