Anti-Dandruff Actives Explained: Zinc Pyrithione, Piroctone Olamine, and the Alternatives

Anti-dandruff shampoo is the category where a formulator most often has to tell a brand that its favourite active cannot be sold in a market it wants to enter. The reason is that dandruff actives sit on the line between cosmetic and drug, and the regulators of the EU, the US, and ASEAN have drawn that line in different places. This post explains what dandruff is, how each active works, and what each major market allows, with the limits taken from the primary regulations as they stand in September 2026.

What dandruff actually is

Dandruff and seborrheic dermatitis share a cause that depends on three things together: sebum, the metabolism of Malassezia yeasts that live on everyone's scalp, and individual susceptibility. Malassezia globosa and Malassezia restricta are the dominant species on dandruff-affected scalps. They cannot make their own fatty acids, so they secrete lipases that break down sebum triglycerides, consume the saturated fatty acids, and leave unsaturated ones such as oleic acid on the skin. In susceptible people, oleic acid alone is enough to trigger the flaking and irritation we call dandruff.

That mechanism explains why the effective actives fall into two families: antifungals that reduce the Malassezia population, and keratolytics that loosen and remove the flakes the yeast provokes. A good anti-dandruff shampoo often combines one of each, and everything else in the formula, including the surfactant system and the conditioning agents, has to be built around them.

The antifungal actives

Zinc pyrithione (ZPT)

The most widely used anti-dandruff active for decades, effective and inexpensive, and the one with the most complicated regulatory position.

• EU: banned. Commission Regulation (EU) 2021/1902 added zinc pyrithione to Annex II of the Cosmetics Regulation, applying from 1 March 2022, following its classification as a category 1B reproductive toxicant. The regulation records that an exemption was refused because suitable alternatives for anti-dandruff use exist. Before the ban it was permitted at up to 1% in rinse-off hair products.
• US: permitted as an over-the-counter drug active under the FDA's dandruff monograph, 21 CFR 358.710, at 0.3% to 2% in products applied and then washed off, and 0.1% to 0.25% in leave-on products.
• ASEAN: not banned. The ASEAN Cosmetic Directive keeps zinc pyrithione at up to 1.0% in rinse-off hair products and 0.1% in leave-on hair products, with full compliance with the latest consolidated amendments due by May 2026.

The practical consequence: a ZPT shampoo made for Southeast Asia, the Gulf, or the US cannot be shipped to the EU. Brands selling in both need either two formulas or a single formula built on a different active.

Piroctone olamine

The active most EU brands moved to after the ZPT ban. It chelates iron in the fungal cell and disrupts energy metabolism, and it is stable across the pH range of a typical shampoo. In the EU it is listed in Annex V, entry 35, at up to 1.0% in rinse-off products and 0.5% in leave-on products. It is not an FDA monograph active, so in the US it can be used as a cosmetic ingredient but the product cannot make a drug-style dandruff treatment claim on the strength of it.

Climbazole

An imidazole antifungal with two separate EU entries, which is the source of frequent confusion. As a preservative, Annex V entry 32 limits it to 0.5% in rinse-off shampoo. As an anti-dandruff active, Annex III entry 310 permits up to 2.0% in rinse-off anti-dandruff shampoo, on condition that the anti-dandruff purpose is apparent from the product's presentation. Both entries were set by Regulation (EU) 2019/698. Climbazole is usually paired with a second active rather than used alone.

Ketoconazole

A pharmaceutical antifungal, and in most markets a drug. In the EU it is a prohibited cosmetic ingredient, Annex II entry 1528. In the US it is sold over the counter at 1% under an approved drug application (the original Nizoral A-D shampoo approval dates from 1997), not under the cosmetic rules and not under the monograph. A contract manufacturer certified for cosmetics cannot make a ketoconazole shampoo; it needs a pharmaceutical licence.

Selenium sulfide

An older antifungal that also slows epidermal turnover. In the EU it is permitted under Annex III entry 49 at 1% in anti-dandruff shampoos, with the warnings "contains selenium disulphide" and "avoid contact with eyes or damaged skin". In the US the monograph allows 1%, or 0.6% in micronised form. It has a characteristic odour and can discolour light hair, which limits its use in premium products.

The keratolytic actives

Salicylic acid

Loosens the bonds between corneocytes so flakes shed evenly rather than in visible clumps. It is often the second active alongside an antifungal. In the EU, Annex III entry 98 allows up to 3.0% in rinse-off hair products, with conditions from Regulation (EU) 2019/1966: not for children under three years except in shampoos, not in applications that could be inhaled, and a warning that it is not to be used in preparations for children under three. In the US the monograph range for dandruff is 1.8% to 3%.

Coal tar

Effective but largely abandoned in cosmetics. Crude and refined coal tars are prohibited in EU cosmetics under Annex II entry 420. In the US, coal tar remains a monograph active at 0.5% to 5% for dandruff, seborrheic dermatitis, and psoriasis, with labelling requirements for the source and concentration. We do not formulate with it.

Sulfur

Listed in the US monograph at 2% to 5%. Rarely used in modern shampoo because of odour and formulation difficulty.

What this means for a formulation brief

1. Name the markets first. The active is chosen by the markets the product will be sold in, not the other way round. A brand selling in the EU and the US with one formula has, in practice, a choice between piroctone olamine with salicylic acid, or a claim strategy that differs by market.
2. Decide whether you are making a cosmetic or a drug. In the US, a product that claims to treat dandruff is an OTC drug and must use a monograph active at a monograph concentration, with drug labelling. A cosmetic "scalp care" shampoo can use piroctone olamine but must keep its claims cosmetic. That distinction drives the factory registration, the label, and the testing.
3. Expect the surfactant system to change. Antifungal actives, particularly ZPT, interact with anionic surfactants and can be deactivated or lost to the rinse. The deposition system, the thickener, and the conditioning polymers are chosen around the active. Our post on surfactant selection explains the trade-offs.
4. Plan the stability and efficacy work. Stability testing has to confirm the active's concentration through shelf life, not just the product's appearance. Efficacy claims need their own substantiation. Our guide to stability testing covers the programme.
5. Check the preservative interaction. Some anti-dandruff actives have antimicrobial activity of their own, but a shampoo still needs a preservative system that passes challenge testing in the final pack, as described in preservative systems explained.

Sources

The EU limits above are taken from the consolidated text of Regulation (EC) No 1223/2009 as of 1 September 2025 and the amending regulations (EU) 2019/698, 2019/1966, and 2021/1902. The US figures are from 21 CFR 358.710. The ASEAN position is from the consolidated ASEAN Cosmetic Directive amendments adopted through the 42nd ASEAN Cosmetic Committee meeting. The mechanism summary follows Dawson (2007) and Park, Park and Jung (2021). Regulations change; confirm the current text before finalising a formula.

HE Manufacturing develops and manufactures scalp care and anti-dandruff shampoos for brands selling in Southeast Asia, the Gulf, the US, and the EU. To discuss an active and a market, send us your brief or read how we approach OEM hair care manufacturing.