Zinc pyrithione

Anti-dandruff agent0.5–2%

A long-established scalp-care active that helps control visible flaking, used in rinse-off shampoos for decades.

What it is

Zinc pyrithione has been a mainstay of shampoos for a flaky scalp for decades. It is a fine powder that stays on the scalp after rinsing, so flakes are visibly reduced and the scalp feels cleaner with regular use. It suits rinse-off shampoos and conditioners.

Good for

Flaky scalpVisible flakesTight scalp

How it works

Zinc pyrithione particles deposit on the scalp and release pyrithione, which slows Malassezia, the scalp yeast linked to visible flaking. Because it works as particles, particle size, deposition polymers and the shampoo base strongly affect results. Products with the same level can perform very differently.

Ratings

Evidence

5/5

Decades of controlled trials on visible scalp flaking.

Gentleness

4/5

Low irritation when rinsed off, and the EU ban is not skin-related.

Formulation difficulty

4/5

Insoluble particles that need suspension and deposition aids.

Cost

2/5

Inexpensive at typical levels.

Popularity

3/5

Still common in shampoos for a flaky scalp, but declining.

Pairs and cautions

Pairs well with

In a routine. Pairing in one formula depends on matching pH windows.

Climbazole
Salicylic acid
Menthol
Zinc carbonate

Take care with

Strong chelators such as EDTACan strip zinc
Soluble ironTurns the product grey-blue
Oxidising agentsSupplier-listed incompatibility

Formulations it suits

Shampoo Conditioner and hair mask

Packaging

Regional considerations

Australia	Scalp products at 2% or less are unscheduled if they carry the TGA's required advisory statements; other uses are Schedule 6 (Schedule 2 if therapeutic). Antifungal or 'cures dandruff' claims make it a therapeutic good.
New Zealand	From 1 January 2026, cosmetics may use it only at 0.1% in leave-on hair products or as a rinse-off preservative (1% hair, 0.5% other). Anti-dandruff shampoos with it fall under the Medicines Act unless Medsafe's exclusion applies.
European Union	Banned in EU cosmetics since 1 March 2022 as a reproductive toxicant, and in Great Britain since 15 October 2022. Piroctone olamine is the usual swap for EU and UK exports.
United States	An OTC anti-dandruff drug active at 0.3–2% in rinse-off and 0.1–0.25% in leave-on products, so US dandruff products are sold as OTC drugs with a Drug Facts panel.

In the lab

Specifications

Typical use level

0.5–2%0525%

pH window

pH 4.5–9.52 acid7 neutral10 alkaline

Solubility

ParticulateWater-dispersible

Sensitive to

LightMetal ions

Anti-dandruff shampoos use 0.5–2%. It is insoluble, so the formula needs a suspending system to keep the particles evenly dispersed.

INCI	Zinc Pyrithione
Also known as	ZPT, Pyrithione zinc
Origin	synthetic

Lab notes

Solubility and phase

Disperse in the water phase as a suspension, often supplied at 48%, since it is practically insoluble in water. Structure with acrylates or glycol distearate to keep particles suspended.

Stability

Keep iron out of the batch, since it turns the product grey-blue, and avoid strong chelators such as EDTA, which can strip zinc. Protect from strong light.

Regulatory, Australia

Permitted in Australian cosmetics, and Schedule 6 in the Poisons Standard except scalp preparations at 2% or less that carry the required advisory statements. Therapeutic use outside that exemption is Schedule 2.

Claims to take care with

Cosmetic only if claims are limited to controlling dandruff by cleansing, moisturising, exfoliating or drying the scalp (TGA Excluded Goods). 'Antifungal', itch-relief or 'treats seborrhoeic dermatitis' claims are therapeutic.