Alopecia areata is an autoimmune type of hair loss, which means the immune system turns on the hair follicle itself. The hair comes out in patches, there is no scarring, and in some people it keeps going until the whole scalp is bare, or the whole body. Oral JAK inhibitors are the pill-form drugs that have been approved over the last few years for the severe end of this condition, and a group of researchers in Australia went looking for what the randomized trial evidence adds up to when you put it all in one place. They registered their plan in advance, searched three research databases from their beginnings through November 28, 2025, and came out with twelve randomized controlled trials covering 4,141 people. The average participant was 35.8 years old and had been in the current episode of hair loss for about 4.8 years. The average starting SALT score was 86. SALT is the Severity of Alopecia Tool, a zero to one hundred measure of how much of the scalp is bare, so a score of 86 means most of these people had very little scalp hair left when they started, and a lower score later means hair came back. At week 24, the odds of getting down to a SALT of 10 or under, which is ninety percent or more coverage, were 5.69 times higher on a JAK inhibitor than on placebo. By week 36 that figure rose to 9.40. For a SALT of 20 or under the odds at week 24 were 7.99 times higher than placebo. Eyebrow and eyelash regrowth improved as well across the agents studied. On safety, people on JAK inhibitors reported more total side effects than people on placebo, with the authors describing most of them as mild and listing acne, upper respiratory infections and headache. There was no statistically significant difference in serious adverse events or in how many people quit the drug because of side effects.

The authors are careful about what those numbers can and cannot carry. An odds ratio is not the share of people who regrow hair, and the paper's own figures make that worth pausing on: in the two large baricitinib trials at week 36, 38.8 percent and 35.1 percent of people on the four milligram dose reached a SALT of 20 or under. Real improvement, and a long way from everybody. Half of the twelve trials were rated as having some concerns for risk of bias, mostly for missing outcome data, with the other half rated low. There are no head to head trials, so this evidence cannot rank one of these drugs against another. The trials used different protocols, doses and assessment timings, and most had short to medium follow-up, so long-term efficacy and safety are still open questions. Eyebrow, eyelash and satisfaction results were measured with so many different tools that the authors could not pool them statistically and had to describe them instead. They also could not formally test for publication bias, because there were too few studies and several shared a placebo group, so they say it cannot be ruled out. One limit matters a great deal for anyone sitting across from a client: all but one of these trials only enrolled people whose current episode of hair loss had run eight to ten years or less, on the understanding that very long-standing loss may not be reversible, so the authors state plainly that their findings do not generalize to long-standing hair loss. On the FDA boxed warning that sits on this drug class for cardiovascular events, clots and malignancy, the authors note it came from post-marketing data in older rheumatoid arthritis patients who already had cardiovascular risk factors, a group quite different from the younger and generally healthier people treated for alopecia areata. They still call for ongoing long-term safety monitoring in this population rather than treating the question as closed.

Here's the study: Morriss S, Foo CH, Lin E, et al. Efficacy and safety of oral Janus kinase inhibitors in adults and adolescents with alopecia areata: a systematic review and meta-analysis of randomised controlled trials. American Journal of Clinical Dermatology, 2026;27(5):925-943. doi:10.1007/s40257-026-01060-z. Indexed on PubMed (PMID 42521957). Read the full text here.

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