Researchers followed 42 people with seborrheic dermatitis, the medical name for the flaking, itching and redness most people call dandruff. Everyone used a medicated shampoo for two weeks first. After that, the group was split at random for eight more weeks, with some staying on the medicated shampoo and the rest switching to a plain one. Along the way the researchers swabbed scalps to track what was living on them, including Malassezia, a yeast that sits on almost everyone's scalp and is thought to play a part in dandruff.

Over those eight weeks the group that stayed on the medicated shampoo saw flaking drop by 56 percent, while flaking in the plain shampoo group more than doubled. Redness and itch both improved in the medicated group, and the yeast counts stayed lower there too. Three things are worth knowing alongside those numbers. The study is small at 42 people. Every author works for Pierre Fabre, the company that makes the shampoo being tested. And the trial was registered with the public trial registry after it had already been run, which means the outcomes being measured were not locked in publicly before the researchers started measuring them.

Here's the study: Maître M, Baradat S, Froliger M, et al. Scalp Microbiome Dynamics Can Contribute to the Clinical Effect of a Novel Antiseborrheic Dermatitis Shampoo Containing Patented Antifungal Actives: A Randomized Controlled Study. Dermatology and Therapy, 2025. Read it here

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