A group of dermatologists writing in the International Journal of Dermatology went back through the published research on a question that has picked up real momentum lately. Can changing your gut improve alopecia areata? Alopecia areata is an autoimmune form of hair loss, meaning the immune system turns on the hair follicle and hair comes out in patches. The gut microbiome is the population of bacteria living in the digestive tract, and the theory under review is that when that population shifts out of balance, the inflammation that follows might feed the disease. The authors found roughly a dozen studies, most of them small, and most of them snapshots taken at a single moment rather than people followed over time. The findings did not line up. Some reported less bacterial variety in people with alopecia areata. Others found no meaningful difference. Several teams proposed a specific bacterial pattern that marks the condition, and other teams could not reproduce it.

They also looked at what happened when researchers tried to change the gut on purpose. In one study of people with advanced alopecia areata, a Mediterranean diet did nothing for 19 of the 20 participants and had a minimal effect on the last one. Probiotic research is thin, and one randomized controlled study showed no significant benefit. There are a few case reports of hair regrowing after a fecal microbiota transplant, a procedure that moves gut bacteria from a donor into a patient, and the authors are careful with those. Those patients were being treated for gut infections at the time, so the regrowth may have happened on its own, and of the two cases most often cited, only one saw improvement big enough to see. Their conclusion is that no causal link between gut imbalance and alopecia areata has been established, that clinical excitement may be outpacing the evidence, and that microbiome testing and microbiome-directed treatments should not be recommended to patients right now. They call for longer, larger studies before anyone draws a line.

Here's the study: McMullen E, Abdel Hafeez D, Pai N, Mainville L, Dumont S, Julanon N, Shenderey R, Xiong G, Towheed S, Donovan J. The Gut Microbiome as a Therapeutic Target in Alopecia Areata: Not Yet Part of the Patient Treatment Plan. International Journal of Dermatology, 2026;65(10):2001-2004. doi:10.1111/ijd.70437. Read the full text here.

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