Skip to main content

Antimicrobials

Zinc pyrithione

Also listed as pyrithione zinc, ZPT

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.

Strong evidenceTypical strength: 0.3-2% in rinse-off shampoo (US; often 1%); banned in EU cosmetics

What it is

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.

How strong is the evidence?

Strong evidence

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.

What it's used for, checked

Controls dandruff

Holds up

Effective with regular use, 2-3 times a week or more; flakes return when you stop.

Treats seborrhoeic dermatitis of the scalp

Holds up

Helps mild cases; ketoconazole is somewhat stronger.

Prevents hair loss

Unproven

Dandruff control is not a hair-loss treatment.

Works well with

  • piroctone-olamine

Who should be careful

  • Leave the lather on the scalp for a few minutes before rinsing; keep it out of the eyes.
  • Stop if the scalp becomes irritated. See a clinician if flaking is thick, red, or spreads to the face or body, or if a medicated shampoo has not helped after a few weeks.
  • Pregnant people who want to minimise exposure can choose another dandruff active; this is a precaution based on animal data, not evidence of harm from shampoo.

The studies

Every citation is checked against its PubMed record.

  1. A multicenter randomized trial of ketoconazole 2% and zinc pyrithione 1% shampoos in severe dandruff and seborrheic dermatitis.
    Pierard-Franchimont C, Goffin V, Decroix J, Pierard GE · Skin Pharmacol Appl Skin Physiol · 2002 · RCT (open, multicentre)

    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.