Is ketoconazole shampoo better than zinc pyrithione for dandruff?

Slightly, on the evidence that exists. In the one multicentre randomised trial that compared them head to head in severe dandruff, ketoconazole 2% improved total dandruff severity by 73% at week 4 versus 67% for zinc pyrithione 1%, and recurrence after stopping was significantly lower with ketoconazole. Two cautions: the trial tested the 2% strength, which is prescription-only in the US, and Cochrane graded the zinc pyrithione evidence base as very low quality.

What did the ketoconazole versus zinc pyrithione trial actually find?

It was an open, randomised, parallel-group multicentre trial in severe dandruff and seborrheic dermatitis of the scalp, published in Skin Pharmacology and Applied Skin Physiology in 2002. It used a 2-week run-in, a 4-week treatment phase and a 4-week treatment-free follow-up, with 343 subjects recruited and roughly 171 assigned to ketoconazole 2% and 160 to zinc pyrithione 1%. At week 4 the total dandruff severity score had improved 73% with ketoconazole and 67% with zinc pyrithione. Recurrence during follow-up was significantly lower after ketoconazole, and side effects were minimal in both arms.

Is over-the-counter Nizoral the same strength as the trial used?

No. In the United States over-the-counter ketoconazole shampoo is 1%; the 2% strength is prescription-only. The head-to-head trial against zinc pyrithione used 2%. A separate comparison of ketoconazole 1% against 2% found 2% significantly better at reducing flaking and Malassezia density at weeks 2 and 4. So the 73% figure should not be read as the expected result from the bottle on the shelf.

Does zinc pyrithione work at all?

Yes - it is FDA-recognised for dandruff control at 0.3 to 2 percent in a wash-off product, and in the head-to-head trial it delivered a 67% improvement in dandruff severity at four weeks. The honest caveat is that Cochrane's 2015 review of topical antifungals for seborrhoeic dermatitis graded the zinc pyrithione evidence as very low quality, meaning the confidence in the size of its effect is poor, not that the effect is absent.

Why does Head & Shoulders in Europe not contain zinc pyrithione?

Zinc pyrithione was classified as a category 1B reproductive toxicant under EU CLP rules, which triggered an automatic prohibition in cosmetics under Commission Regulation (EU) 2021/1902, effective 1 March 2022. European and UK formulations were reformulated, commonly to piroctone olamine. The United States did not follow, so zinc pyrithione remains standard in North American products. This is a regulatory hazard classification, not a finding that the shampoo failed to work.

Nizoral vs Head & Shoulders: The Trial Numbers Nobody Quotes

Researched, not tested. We have not personally used this product or protocol. This page answers the question from published sources, every one of which is linked. Our first-hand testing lives in reviews.

Evidence: mixed Mixed evidence — the data are limited, indirect, inconsistent or formulation-specific.

Almost every page ranking for this comparison asserts that ketoconazole is stronger and moves on. There is an actual head-to-head trial behind that claim, it has actual numbers in it, and the numbers are more interesting than the assertion — partly because the gap is narrower than you would guess, and partly because the trial did not test the bottle most people end up buying.

The trial

The comparison people argue about has one good head-to-head study behind it: A multicenter randomized trial of ketoconazole 2% and zinc pyrithione 1% shampoos in severe dandruff and seborrheic dermatitis, published in Skin Pharmacology and Applied Skin Physiology in 2002 (PubMed 12476017 · full text PDF).

Design: open, randomised, parallel-group, multicentre. A 2-week run-in, a 4-week treatment phase, then a 4-week follow-up with no treatment. 343 subjects were recruited, with roughly 171 assigned to ketoconazole 2% and 160 to zinc pyrithione 1%.

The results, which almost nobody quotes:

	Ketoconazole 2%	Zinc pyrithione 1%
Improvement in total dandruff severity score at week 4	73%	67%
Recurrence after stopping	Significantly lower	Higher
Overall clearing at end of treatment and follow-up	Favoured ketoconazole	—
Side effects	Minimal	Minimal

The authors concluded ketoconazole 2% was significantly superior. That conclusion is fair. But look at the size of it: six percentage points on the severity score. Both shampoos worked, and worked well, on people with severe dandruff.

The more useful difference is the second row. The gap widened after treatment stopped. Ketoconazole held the result better than zinc pyrithione did. If your complaint is “it comes back the week I stop,” that row is the one that speaks to you.

The catch nobody mentions

The trial used ketoconazole 2%. In the US, over-the-counter ketoconazole shampoo is 1%; 2% is prescription-only.

And the two strengths are not interchangeable. A separate Karger study comparing them found that at both 2 and 4 weeks, ketoconazole 2% was significantly superior to 1% for reducing flaking and Malassezia density.

So the honest chain is: 2% beat zinc pyrithione, and 2% beat 1%. Nobody has run OTC ketoconazole 1% head to head against zinc pyrithione 1%. The 73% figure is not a promise about the bottle you can buy without a prescription.

What 1% does have is a placebo-controlled trial of its own: twice-weekly ketoconazole 1% shampoo gave a good or excellent result in 74% of patients versus 20% on placebo at 2 weeks, and 80% versus 23% at 4 weeks. It works. It is just not the strength that won the comparison.

What Cochrane says about the evidence

Cochrane’s 2015 review of topical antifungals for seborrhoeic dermatitis picked up the same trial and reported a lower remission-failure rate for ketoconazole than zinc pyrithione, RR 0.85 (95% CI 0.72 to 0.99) — a real but modest effect whose confidence interval only just clears 1.0.

The review’s wider verdicts matter more than that one number:

Evidence for ketoconazole versus placebo or a steroid: low quality
Evidence for ciclopirox versus placebo: moderate quality
Evidence for zinc pyrithione: very low quality
Limited evidence that any agent is more effective than others within the same class
Very few studies assessed anything beyond four weeks

That last point deserves emphasis. Dandruff is a lifelong relapsing condition and the literature almost entirely stops at one month. Anyone telling you which shampoo is better over years is not reading a study.

This is why the page is rated mixed and not strong. There is one decent head-to-head trial, and it is thinner underneath than the confident internet consensus suggests.

The Head & Shoulders footnote

If you are comparing bottles internationally, note that Head & Shoulders in Europe and the UK largely no longer contains zinc pyrithione. It was classified as a category 1B reproductive toxicant under EU CLP rules, which triggered an automatic cosmetics prohibition under Commission Regulation (EU) 2021/1902, effective 1 March 2022. Formulations were switched, commonly to piroctone olamine.

Worth stating plainly: that is a hazard classification driving a regulatory rule. It is not a finding that the shampoo stopped working, and the US has not followed. But it does mean “Head & Shoulders” names two different products depending on where you are standing.

What we would actually do

Mild, occasional flaking: zinc pyrithione or selenium sulfide 1%. Cheap, effective enough, easy to keep using.
Persistent flaking, or it returns fast after you stop: ketoconazole 1% OTC, used at the label’s contact time, twice weekly for four weeks.
Still there after four weeks, or severe: this is the point to ask a doctor about ketoconazole 2% or ciclopirox, rather than buying a fourth bottle.
Thick adherent scale: descale with salicylic acid first, or the antifungal cannot reach the skin. See scalp build-up vs dandruff.

All of these are commodity products. Price differences between brands carrying the same active at the same percentage are packaging.

If the scalp is painful, losing hair, or crusting rather than flaking, the comparison above is not your question — read crust on your scalp instead.

Sources

Researched, not tested. We have not run these shampoos against each other and this is not a product review. General information, not medical advice.