What actually works on dandruff? Antifungal shampoos, the trial evidence shows

The flaking most people call dandruff sits at the mild end of seborrhoeic dermatitis, the chronic inflammatory skin condition that produces scaling and redness on the scalp and face [s1] [s2]. That matters for anyone standing in the shampoo aisle, because the best trial evidence for the active ingredients in medicated shampoos comes from studies of seborrhoeic dermatitis — and two Cochrane reviews of that condition give a reasonably clear answer about which ingredients earn their place and which claims outrun the data.

Antifungals: the strongest signal

The reason an antifungal turns up in an anti-dandruff shampoo is that a yeast on the skin drives the flaking, and the drugs that suppress it reduce the scale. The Cochrane review of topical antifungals pooled 51 studies with 9052 participants [s1]. Ketoconazole 2% — the ingredient in many pharmacy shampoos — carried a 31% lower risk of failed clearance of the rash than placebo at four weeks (risk ratio 0.69, 95% confidence interval 0.59 to 0.81, eight studies) [s1]. To put that in context, the review noted that a median of 69% of people in the placebo groups did not clear, so this is a real but partial effect, not a cure [s1]. Whether ketoconazole itself causes more side effects than placebo stayed uncertain, resting on very low-quality evidence (risk ratio 0.97, 0.58 to 1.64) with substantial variation between studies [s1]. Ciclopirox 1%, the other common medicated-shampoo agent, also beat placebo, with a failed-remission risk ratio of 0.79 (0.67 to 0.94) [s1]. Ketoconazole and ciclopirox performed similarly to each other (risk ratio 1.09) [s1].

Antifungal or steroid?

Some scalps get prescribed a topical steroid instead. Here the two reviews line up usefully. Ketoconazole produced remission rates similar to steroids (risk ratio 1.17, 95% confidence interval 0.95 to 1.44), but with 44% fewer side effects (risk ratio 0.56, 0.32 to 0.96) [s1]. The separate review of anti-inflammatory treatments, covering 36 trials and 2706 participants, confirmed steroids work — total clearance was more common with a topical steroid than placebo in short-term trials (risk ratio 3.76, 1.22 to 11.56) — and found no meaningful difference between mild and strong steroids [s2]. It also found steroids and azole antifungals gave comparable short-term clearance (risk ratio 1.11, 0.94 to 1.32) [s2]. The practical reading is that an antifungal and a steroid are broadly matched on clearing the flaking, but the antifungal tends to come with fewer adverse effects [s1].

What the evidence does not settle

Both reviews are candid about their limits, and those limits bear directly on how a shopper should read a shampoo bottle. In the antifungal review, very few studies looked beyond four weeks, so the evidence speaks to short-term clearance, not to controlling a lifelong, relapsing condition [s1]. No study assessed quality of life, and only one reported on how consistently people used the treatment [s1]. The reviewers also flagged that 24 of the 51 trials had a likely conflict of interest, such as pharmaceutical-company funding [s1]. The anti-inflammatory review echoed the pattern: most studies were small and lasted four weeks or less, with risk of bias most often unclear because of poor reporting [s2]. Neither review can tell you which product keeps flaking away over a year.

The bottom line

Stripped of marketing, the evidence supports a simple hierarchy. The medicated-shampoo ingredients with the best backing are the antifungals ketoconazole and ciclopirox, both shown to clear scaling better than placebo in short-term trials, with ketoconazole roughly as effective as a topical steroid but gentler [s1] [s2]. What the trials do not establish is any long-term cure, any quality-of-life benefit, or a clear winner among the antifungals themselves [s1]. Because seborrhoeic dermatitis relapses, dandruff is best thought of as controlled rather than cured — the shampoos manage it while used, and the flaking tends to return when they stop [s1].

The reviews studied diagnosed seborrhoeic dermatitis in adolescents and adults [s2], which is also the signpost for when the pharmacy aisle is the wrong place to be: a scaly, red or itchy scalp that fails to respond to a medicated shampoo, spreads, or is severe deserves a clinician's assessment, because several skin conditions flake. This article reports what the evidence shows, not what any individual should use.