Piroctone olamine

What it is

Piroctone olamine (PO, sold as "Octopirox") is the ethanolamine salt of a hydroxypyridone antifungal. It is used as an anti-dandruff ingredient in shampoos, and the rules on how it may be labelled differ between regions.

How it works

It inhibits Malassezia yeast and also binds iron, a pathway shared with ciclopirox. In a 2024 study, a PO shampoo reduced the relative abundance of Malassezia and Staphylococcus capitis, raised Cutibacterium acnes, and lowered oxidative-stress, protease, urease and lipase gene signals on dandruff scalps (Hu 2024, industry-affiliated).

What the studies show

• In a double-blind half-head trial of 19 people over about 4 weeks, PO 0.75% plus salicylic acid 2% and zinc pyrithione 1% both cut dandruff strongly, with the PO combination slightly better on severity and area (Loden 2000).
• A double-blind randomized trial found a non-tar shampoo (salicylic acid, PO and elubiol) at least as effective as a coal tar shampoo, with lower Malassezia counts (Pierard-Franchimont 2000).
• In a split-head trial, PO 0.5% plus climbazole 0.45% gave a dandruff reduction comparable to zinc pyrithione 1%, and 90% approved of its itch reduction (Schmidt-Rose 2011).
• A Procter & Gamble formulation study found better retention of PO on the scalp improved anti-dandruff efficacy (Johnson 2023).
• A 3-week PO shampoo study improved flaking versus control and shifted the scalp microbiome toward a healthy pattern (Hu 2024).
• In 20 people with moderate to severe scalp seborrheic dermatitis, a salicylic acid, PO and zinc pre-gel plus cleanser was used for 4 weeks plus 12 weeks of maintenance. It was a small uncontrolled cohort (Ge 2025).

Evidence is fairly good: several controlled comparisons, but mostly small or manufacturer-run, and rarely PO alone against placebo.

How it's used in studies

Shampoos contained 0.5-0.75% PO, often with climbazole or salicylic acid, used two to three times a week for 3-4 weeks.

Side effects and safety

Irritation was low in trials. Tolerance data are for mixed formulas, since PO is usually combined with other actives.

Bottom line

A sensible option for sensitive scalps or for people who dislike the smell or residue of other actives. It was equivalent to zinc pyrithione in the head-to-head data above. Look for formulas that pair PO with a keratolytic if scale is thick. PO-alone versus placebo trials are scarce, and hair-growth claims on some "anti hair-loss" PO shampoos lack independent trial support.