Encyclopedia · anti dandruff
Zinc pyrithione
The most widely used anti-dandruff shampoo ingredient, proven in large trials to cut flaking, though most of those trials were run by the companies that sell it.
What it is
Zinc pyrithione (ZPT) is a zinc complex of pyrithione, an antifungal and antibacterial agent. Typical anti-dandruff shampoos contain about 1%, the concentration studied in the pooled analysis below. Check the pack for how it is classified where you live.
How it works
ZPT acts as a copper ionophore: it carries copper into yeast cells, which inactivates iron-sulfur cluster proteins and stops growth. This was shown in baker's yeast and then confirmed as a growth-inhibition mechanism in Malassezia globosa, a scalp fungus (in vitro) (Reeder 2011). Delivery matters: formulations that put more ZPT on the scalp performed better in industry trials (Schwartz 2013).
What the studies show
- A pooled analysis of 17 half-head double-blind trials in Asia (2,088 people) found 1% ZPT beat a non-anti-dandruff shampoo at every week of 4 weeks. The 4-week flake-score gap was larger in men (-17.5) than women (-11.1) (Collins 2018, Unilever authors).
- In 331 people with severe dandruff or seborrheic dermatitis, ketoconazole 2% was significantly better than ZPT 1%, with fewer recurrences (Pierard-Franchimont 2002).
- In a double-blind half-head trial of 19 people, a piroctone olamine 0.75% plus salicylic acid 2% shampoo cut dandruff strongly, slightly better than ZPT 1% (Loden 2000).
- A split-head trial found piroctone olamine 0.5% plus climbazole 0.45% comparable to ZPT 1% for dandruff reduction (Schmidt-Rose 2011).
- A Procter & Gamble trial found a ZPT formulation with higher bioavailability beat a ZPT plus climbazole product on flaking (Schwartz 2013).
- Oxidative damage is part of dandruff, and a ZPT shampoo improved scalp condition and hair-quality markers (Schwartz 2015).
- As a maintenance shampoo after remission, ZPT and selenium disulfide showed no significant difference in time to relapse (Hasanbeyzade 2023).
Funding caveat: the pooled analysis and the climbazole study are from Unilever authors and the potentiated ZPT work is from Procter & Gamble. The trials are well designed, but the sponsors make ZPT shampoos.
How it's used in studies
Trials used 1% ZPT shampoo two to three times a week for 4 weeks, with half-head or parallel designs.
Side effects and safety
ZPT is generally well tolerated, with occasional scalp irritation or dryness. It was not associated with hair loss in these trials.
Bottom line
A reliable, cheap first step for ordinary dandruff. Men appeared to respond more strongly in pooled data. If ZPT stops working after months, switching actives (ketoconazole, selenium sulfide, piroctone olamine) is reasonable, although there is no good evidence that Malassezia becomes resistant. Many ZPT shampoos contain silicones for slip, which can feel heavy on fine hair. Most pooled data come from Asian cohorts and from industry, and few trials report results by curl pattern. Discuss with a doctor.
Fun facts
- ZPT kills dandruff yeast by smuggling copper into it, which wrecks the iron-sulfur proteins the yeast needs to grow (Reeder 2011).
Studies 8
Collins LZ et al. Sex-related differences in response to zinc pyrithione shampoo vs. non-anti-dandruff shampoo. Int J Cosmet Sci. 2018
Tested: 1% zinc pyrithione versus a non-anti-dandruff shampoo
Result: Zinc pyrithione beat the control shampoo at all weeks; the 4-week flake-score gap was larger in men (-17.5) than women (-11.1). Unilever authors.
Read the study ↗Reeder NL et al. Zinc pyrithione inhibits yeast growth through copper influx and inactivation of iron-sulfur proteins. Antimicrob Agents Chemother. 2011
Result: Zinc pyrithione carries copper into yeast cells and inactivates iron-sulfur proteins, stopping growth; shown in baker's yeast and confirmed in the scalp fungus Malassezia globosa.
Read the study ↗Piérard-Franchimont C et al. A multicenter randomized trial of ketoconazole 2% and zinc pyrithione 1% shampoos in severe dandruff and seborrheic dermatitis. Skin Pharmacol Appl Skin Physiol. 2002
Tested: ketoconazole 2% versus zinc pyrithione 1% shampoo (open randomised)
Result: Ketoconazole was significantly superior in severe cases, with fewer recurrences; both were well tolerated.
Read the study ↗Lodén M et al. The antidandruff efficacy of a shampoo containing piroctone olamine and salicylic acid in comparison to that of a zinc pyrithione shampoo. Int J Cosmet Sci. 2000
Tested: piroctone olamine 0.75% plus salicylic acid 2% versus zinc pyrithione 1% shampoo (double-blind, half-head)
Result: Both strongly cut dandruff; the piroctone olamine combination was slightly better on severity and area.
Read the study ↗Schmidt-Rose T et al. Efficacy of a piroctone olamine/climbazol shampoo in comparison with a zinc pyrithione shampoo in subjects with moderate to severe dandruff. Int J Cosmet Sci. 2011
Tested: piroctone olamine 0.5% plus climbazole 0.45% versus zinc pyrithione 1% (split-head)
Result: Comparable dandruff reduction and anti-fungal effect; 90% approved of the itch reduction with the piroctone olamine and climbazole shampoo.
Read the study ↗Schwartz JR et al. Therapeutic efficacy of anti-dandruff shampoos: a randomized clinical trial comparing products based on potentiated zinc pyrithione and zinc pyrithione/climbazole. Int J Cosmet Sci. 2013
Tested: potentiated zinc pyrithione versus zinc pyrithione plus climbazole shampoo
Result: The zinc pyrithione formulation with higher bioavailability beat the dual-active product on flaking. Procter & Gamble study.
Read the study ↗Show 2 more studies
Schwartz JR et al. The role of oxidative damage in poor scalp health: ramifications to causality and associated hair growth. Int J Cosmet Sci. 2015
Tested: potentiated zinc pyrithione shampoo
Result: Oxidative damage is part of dandruff; the zinc pyrithione shampoo improved oxidative markers, scalp condition and hair quality markers. Procter & Gamble study.
Read the study ↗Hasanbeyzade S et al. The Effects of Zinc Pyrithione and Selenium Disulfide Shampoos on the Lesion-free Period After Treatment in Patients with Seborrheic Dermatitis. J Clin Aesthet Dermatol. 2023
Tested: zinc pyrithione versus selenium disulfide shampoo as maintenance
Result: No significant difference in time to relapse.
Read the study ↗Related
- KetoconazoleAn antifungal shampoo ingredient that is among the best-proven treatments for dandruff and, with much weaker evidence, a possible add-on for pattern hair loss.
- Piroctone olamineA gentle anti-dandruff ingredient common in European shampoos, with trial results roughly equal to zinc pyrithione but mostly from manufacturers.
- Selenium sulfideAn old, inexpensive anti-dandruff active that new trials suggest works about as well as ketoconazole and has been tested across all curl types.
- ClimbazoleA cosmetic azole antifungal used mostly as a booster next to zinc pyrithione or piroctone olamine, with thin evidence on its own.
- DandruffDandruff is a common, chronic flaking of the scalp driven by yeast, skin oil and your skin's sensitivity, and an antifungal shampoo controls it well as long as you keep using it.