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Zinc Pyrithione

B
lead outcome
Topical (scalp, rinse-off at 1%): visible…
grades vary by outcome ↓
Small molecule (non-peptide)
also called — pyrithione zinc · ZPT · zinc omadine
anti-dandruffscalppreservative
Safety

Zinc pyrithione carries a harmonised CLP classification as toxic for reproduction, category 1B, introduced by Commission Delegated Regulation (EU) 2020/1182. This classification, not a finding of harm in shampoo use, is what removed it from EU cosmetics. Anyone who is pregnant, planning a pregnancy or simply prefers to avoid substances carrying a reproductive hazard classification has a straightforward alternative available, since equally effective actives remain lawful in every market.

In brief

A zinc compound used against dandruff for more than sixty years, and the register's sharpest illustration that safe and lawful are different questions. In randomised head-to-head shampoo trials, 1% zinc pyrithione controlled visible flaking effectively, performing on par with the formulations tested against it. The EU Scientific Committee on Consumer Safety reviewed it and concluded in 2020 that it was safe for exactly that use. It is nonetheless prohibited in EU cosmetics from 1 March 2022, because a harmonised classification as toxic for reproduction category 1B triggered a legal test requiring proof that no suitable alternative existed, and that proof was not available. It remains lawful in the United States, where labels carry it as Pyrithione Zinc. So a European reading an American recommendation is being pointed at something they cannot lawfully buy, and the usual explanation for why is wrong.

Legal standing, by region
European Union
Prohibited in cosmetic products

Prohibited in all cosmetic products placed on the EU market from 1 March 2022. Commission Regulation (EU) 2021/1902 of 29 October 2021 amended Annexes II, III and V to Regulation (EC) No 1223/2009, adding zinc pyrithione to the Annex II list of prohibited substances as entry 1670 and deleting its previous permissions. Before that date it was allowed under Annex V as a preservative at up to 1.0% in rinse-off hair products and 0.5% in other rinse-off products, and under Annex III at up to 0.1% in leave-on hair products when not used as a preservative. The prohibition applied to stock already on shelves, not only to new products.

United States
Lawful over-the-counter active

Remains lawful in the United States, where it is a recognised over-the-counter anti-dandruff active and appears on labels as Pyrithione Zinc. Products sold in the US therefore continue to contain it at concentrations that have not been permitted in the EU since March 2022.

Evidence, by outcome
How we grade →

An honest grade per outcome — drawn from the evidence, not any catalogue. Hype and undemonstrated marketing claims grade low.

OutcomeEvidence base · effectGrade
Topical (scalp, rinse-off at 1%): visible flaking control
Small sample sizes, and both studies were designed to evaluate a competitor formulation with zinc pyrithione as the benchmark rather than the subject. Dandruff is relapsing: this is control while in use, not resolution.
Two randomised head-to-head shampoo trials in which 1% zinc pyrithione served as the active comparator: a double-blind bilateral study over roughly four weeks (Lodén 2000, n=19) and a split-head in-use study in moderate to severe dandruff (Schmidt-Rose 2011), supported by decades of category use. · Highly effective at reducing scaling in both trials, and equally effective as the comparator formulations at reducing the amount of visible dandruff on the scalp.
B
Topical (scalp): itch and subjective scalp comfort
Self-reported and secondary to the scaling endpoints. In the head-to-head work the comparator formulations tended to score at least as well on comfort and combability.
Self-reported outcomes within the same comparative trials, alongside investigator scoring of scaling severity and affected area. · Reported improvement in scalp comfort accompanying the reduction in scaling.
C
Common claim: the EU banned it because it was found unsafe in shampoo
The prohibition followed from a different test. Once classified as toxic for reproduction category 1B under CLP, its use required an exemption under Article 15(2) of the Cosmetics Regulation, and that route needs proof that no suitable alternative exists. That was not demonstrated, so the exemption failed and the substance moved to the prohibited annex. Safe in use and lawful are two separate questions here.
Consumer claim, tested against the regulatory record. · The record says the opposite on the safety question. The Scientific Committee on Consumer Safety concluded in its March 2020 opinion that zinc pyrithione is safe as an anti-dandruff agent in rinse-off hair products up to 1%.
D
Safety (topical, rinse-off)
The reproductive toxicity classification is a hazard classification, which describes the substance rather than a given exposure. It is the reason the substance is no longer lawful in EU cosmetics regardless of the use-level safety conclusion.
SCCS opinion on zinc pyrithione (SCCS/1614/19, adopted March 2020) and the harmonised CLP classification introduced by Commission Delegated Regulation (EU) 2020/1182. · Assessed as safe for the specific rinse-off anti-dandruff use at up to 1%, while carrying a harmonised classification as toxic for reproduction, category 1B.
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Disclosure

Vallydia sells its own cosmetic serums, and some ingredients graded here belong to the same categories as those products. Grades are drawn from the published evidence by the method we publish, and applied to our own ingredients on the same terms — our copper-peptide serum is graded no more kindly than the peptides it competes with. We disclose the interest so you can weigh it.

Trade names shown here (for example Matrixyl, Argireline, Syn-Ake) are the property of their respective owners and are used only to identify the ingredient under discussion. Their appearance implies no affiliation with, or endorsement by, the proprietor.

Evidence changes

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Cosmetic claims boundary
✓ Allowed (appearance / feel)
  • helps control visible flaking on the scalp while in use
  • helps the scalp feel more comfortable alongside reduced scaling
  • used as a rinse-off anti-dandruff active at up to 1% where it remains lawful
✕ Not allowed (medicinal)
  • treats seborrhoeic dermatitis
  • cures dandruff
  • treats scalp psoriasis
  • antifungal treatment

The medicinal-sounding science stays in the reference section; product copy speaks only to appearance/feel (Reg 655/2013). Different fields, never merged.

The honest part

This substance is the clearest case in the register of the gap between safe and lawful. A scientific committee reviewed it and said it was safe for the use it was sold for. It was prohibited anyway, because a hazard classification triggered a legal test that asks a different question, and the industry could not show that no alternative existed. Both facts are true at once, and most coverage reports only one of them.

Identity

Zinc Pyrithione is the zinc complex of 2-mercaptopyridine-N-oxide, an aromatic zinc compound. In cosmetics it has functioned in three roles at once: anti-dandruff agent, antiseborrhoeic agent and preservative, which is why it previously appeared in two separate annexes of the EU Cosmetics Regulation under different conditions depending on which role it was performing.

On United States packaging it is declared as Pyrithione Zinc rather than Zinc Pyrithione. The words are reversed, the molecule is the same, and both forms resolve to this entry.

Development & history

The compound entered anti-dandruff shampoo in the mid twentieth century and became one of the most widely used actives in the category worldwide, anchoring several of the largest shampoo brands on the market.

Its removal from EU cosmetics ran through a chain of decisions rather than a single safety finding. In 2020 the CLP Regulation was amended by Commission Delegated Regulation (EU) 2020/1182, giving the substance a harmonised classification as toxic for reproduction, category 1B. Under the Cosmetics Regulation, a CMR 1A or 1B substance may be used only by exception, and one of the conditions is a documented absence of suitable alternatives. An application was made in 2019 to keep it as an anti-dandruff agent in rinse-off hair products at up to 1%. The SCCS reviewed the safety question and answered it favourably in March 2020. The alternatives condition was the one that failed. Commission Regulation (EU) 2021/1902 followed in October 2021, and the prohibition took effect on 1 March 2022.

Mechanism (as proposed)

Dandruff is associated with colonisation of the scalp by Malassezia yeasts and with the flaking and irritation that accompany it. Zinc pyrithione is proposed to act principally as an antifungal, reducing the Malassezia population on the scalp and with it the scaling response.

A secondary proposal concerns zinc transport. The complex is thought to increase intracellular copper and zinc levels in fungal cells, disrupting iron-sulfur cluster proteins and impairing metabolism. Because the substance is poorly soluble, its performance in a shampoo depends heavily on particle size and on how much of it remains on the scalp after rinsing, which is why substantivity rather than raw concentration tends to distinguish formulations in comparative testing.

Related reading

Our coverage of anti-dandruff shampoos examines the actives in this category side by side. See also our scalp care writing for the broader question of treating the scalp as skin.

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Sources — 3 cited
01Lodén M, Wessman C. The antidandruff efficacy of a shampoo containing piroctone olamine and salicylic acid in comparison to that of a zinc pyrithione shampoo. International Journal of Cosmetic Science. 2000;22(4):285-289. PMID 18503415.
02Schmidt-Rose T, Braren S, Fölster H, Hillemann T, Oltrogge B, Philipp P, Weets G, Fey S. Efficacy of a piroctone olamine/climbazol shampoo in comparison with a zinc pyrithione shampoo in subjects with moderate to severe dandruff. International Journal of Cosmetic Science. 2011;33(3):276-282. PMID 21272039.
03Commission Regulation (EU) 2021/1902 of 29 October 2021 amending Annexes II, III and V to Regulation (EC) No 1223/2009 of the European Parliament and of the Council as regards the use in cosmetic products of certain substances classified as carcinogenic, mutagenic or toxic for reproduction. Official Journal of the European Union, 3 November 2021.
Updated 2026-08-28

Grades reflect the published evidence, not our interest. No dosing, reconstitution, or administration is published for research compounds — that restraint is deliberate.

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Salicylic AcidA
Small molecule (non-peptide)
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