The long-standing anti-dandruff drug in US shampoos. Works well against the yeast behind dandruff, but has been banned in EU cosmetics since 2022.
Zinc pyrithione kills Malassezia, the scalp yeast that drives dandruff and seborrhoeic dermatitis. In the US it is an approved over-the-counter dandruff active: 0.3-2% in rinse-off shampoos and 0.1-0.25% in leave-on products.
The EU banned it from all cosmetics in March 2022 after it was classified as toxic to reproduction (based on animal data), even though the EU's safety committee had judged shampoos up to 1% safe. European anti-dandruff shampoos now mostly use piroctone olamine or climbazole instead.
Decades of randomised trials show zinc pyrithione shampoos reduce dandruff; in a 331-person trial, 1% zinc pyrithione improved severe dandruff by 67% at 4 weeks versus 73% for 2% ketoconazole, which also had fewer relapses. The EU ban reflects a hazard classification from animal studies, not observed harm to shampoo users.
331 people with severe dandruff or seborrhoeic dermatitis: after 4 weeks, zinc pyrithione 1% improved severity scores by 67% and ketoconazole 2% by 73%; ketoconazole also had fewer relapses. Both were well tolerated.