This systematic review assembled 68 studies — 42 randomised trials, 14 open-label extensions and 12 real-world cohorts — covering 15,427 patients treated with JAK inhibitors for atopic dermatitis, psoriasis, vitiligo, alopecia areata and hidradenitis suppurativa.
Oral JAK inhibitors were effective across conditions, with EASI-75 response of 38-73% in atopic dermatitis, PASI-75 of 33-67% in psoriasis, and SALT-50 of 30-62% in alopecia areata. Topical formulations worked for atopic dermatitis and vitiligo but showed limited benefit in alopecia areata, which is a useful negative given how often topical treatment is tried first for hair loss. On safety, upper respiratory infection occurred in 5-14% and herpes zoster reactivation in 1-3%; major cardiovascular events, venous thromboembolism and cancers were rare but did occur.
The comparative conclusions are the part to treat carefully. Selective JAK1 inhibitors appeared to offer the best efficacy-safety balance in atopic dermatitis, and JAK1/2 inhibitors were numerically better in alopecia areata, but that difference did not reach significance. The authors list their own constraints plainly: short controlled trials, under-representation of diverse populations, and reliance on indirect comparison. The practical message is the herpes zoster rate, which is high enough to warrant discussing vaccination before starting in an older or immunosuppressed patient.
- EASI-75 38-73% in atopic dermatitis; PASI-75 33-67% in psoriasis
- Topical JAK inhibitors work in eczema and vitiligo, not in alopecia areata
- Upper respiratory infection 5-14%; herpes zoster reactivation 1-3%
- Comparative rankings rest on indirect comparison and did not reach significance
The statistics, in plain English
The wide response ranges — 38 to 73% for the same outcome in the same disease — reflect real differences between drugs, doses and populations, so a single pooled figure would have been misleading and the authors were right not to give one. Note also that rare serious events cannot be assessed from trials of this length: cardiovascular events and cancers accumulate over years, and controlled follow-up here was measured in months.
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