Baricitinib: Alopecia Areata and Beyond

Key points

Alopecia areata: the immune system attacks hair

Alopecia areata (patchy hair loss) occurs at least once in a lifetime in about 1 person in 50: in a large UK study the lifetime incidence was 2.1% (Thompson AR Br J Dermatol 2024. PMID 39104082^[4]). Hair falls out in round patches, sometimes almost all the hair on the head goes, and with it the eyebrows and eyelashes.

The cause lies in the body's own immune system: its cells mistakenly attack the hair follicle. No scar is left, so the hair can grow back if the attack is stopped (Mateos-Haro M Cochrane Database Syst Rev 2023. PMID 37870096^[5]).

Alopecia affects more than appearance. Among those who had signs of anxiety on the HADS (Hospital Anxiety and Depression Scale) at baseline, these resolved in 47% with good hair regrowth versus 26% without regrowth (Piraccini BM J Dermatolog Treat 2023. PMID 37381691^[6]). This is an association with regrowth, not a direct effect of the pill on the mind.

How baricitinib works

Inside an immune cell, inflammatory signals are relayed by enzymes called Janus kinases (JAK). Baricitinib inhibits two of them — JAK1 and JAK2 (King B N Engl J Med 2022. PMID 35334197^[1]). Inflammatory signals weaken, and the immune attack on the follicle can subside. It is taken as one tablet a day: 2 or 4 mg.

Scalp hair: what the trials showed

Eyebrows and eyelashes

Over 36 weeks on 4 mg, eyebrows regrew fully or almost fully in 44.3% and eyelashes in 46.4% of those with noticeable gaps; on placebo, in 12.6% and 12.4% (Mostaghimi A Br J Dermatol 2025. PMID 40179237^[2]).

By week 52 on 4 mg, among those whose scalp hair regrew, eyebrows recovered in 78.5% and eyelashes in 82.6%. And even when the scalp did not respond, eyebrows and eyelashes came back in almost half (Mostaghimi A Br J Dermatol 2025. PMID 40179237^[2]).

How long the result lasts

The data here are good — provided treatment continues, and they apply to those who responded by the first year. At 2 years about 9 in 10 on 4 mg kept the result (Senna M J Eur Acad Dermatol Venereol 2024. PMID 38391212^[11]), at 3 years 89% on 4 mg and 84% on 2 mg (Senna M J Am Acad Dermatol 2026. PMID 41314424^[3]), and at almost 4 years about 85% (Vleugels RA Dermatol Ther (Heidelb) 2026. PMID 42825995^[12]). Dropouts were not counted in these calculations, and in the 4-year analysis missing data were filled in by a statistical estimate, so the estimate may be slightly inflated.

Rheumatoid arthritis

Baricitinib was first approved for joints, in rheumatoid arthritis: in the European Union since 2017 (EMA, 2017), and in the US since 2018 at a dose of 2 mg (FDA, 2018). The trials below studied the 4 mg dose:

• together with methotrexate, improvement on the ACR20 scale (at least 20%) over 12 weeks occurred in 70% versus 40% on placebo, and more often than with the biologic drug adalimumab (Taylor PC N Engl J Med 2017. PMID 28199814^[14]);
• even when biologic drugs had not helped, improvement occurred twice as often: 55% versus 27% (Genovese MC N Engl J Med 2016. PMID 27028914^[15]);
• in those just starting treatment, baricitinib on its own helped more often than the standard first drug, methotrexate: 77% versus 62% over 24 weeks (Fleischmann R Arthritis Rheumatol 2017. PMID 27723271^[16]);
• at 5 years, joint damage on X-rays had not progressed in 60–66% of those who started on baricitinib versus 41% of those who started on methotrexate (van der Heijde D J Rheumatol 2022. PMID 34526397^[17]).

Atopic dermatitis: itch eases quickly

Itch began to ease as early as the day after the first tablet, and falling asleep became easier from the second day (Buhl T Dermatol Ther (Heidelb) 2021. PMID 33899152^[18]). Together with steroid creams, on 4 mg clear or almost clear skin at 16 weeks was twice as common: 31% versus 15% (Reich K JAMA Dermatol 2020. PMID 33001140^[19]).

The drug has also been studied in children. In atopic dermatitis in 2–17-year-olds, the high dose together with creams outperformed placebo on all main measures (Torrelo A Br J Dermatol 2023. PMID 36999560^[20]), and in juvenile arthritis three quarters of children responded in the open-label part of the trial, and with continued treatment flares occurred less often than after switching to placebo; there were twice as many infections in this trial, and one case of PE (pulmonary embolism) was judged to be related to the drug (Ramanan AV Lancet 2023. PMID 37423231^[21]).

Severe COVID

In the largest trial of patients hospitalized with COVID, 12% died within 28 days on baricitinib versus 14% on usual care; together with similar drugs, data from nine trials show a reduction in mortality of about one fifth (RECOVERY Collaborative Group Lancet 2022. PMID 35908569^[22]). In a double-blind trial the main goal — fewer cases of deterioration — was not met, while 28-day mortality, a secondary goal, was 8% versus 13% (Marconi VC Lancet Respir Med 2021. PMID 34480861^[23]). Together with an antiviral drug, recovery was on average one day faster (Kalil AC N Engl J Med 2021. PMID 33306283^[24]). The World Health Organization gave baricitinib a strong recommendation together with corticosteroids (WHO, 2022).

Type 1 diabetes: an unexpected trial

In type 1 diabetes, the immune system destroys the cells that make insulin. In the BANDIT trial, 91 people whose diabetes had been diagnosed no more than 100 days earlier took baricitinib or placebo. After 48 weeks, more of their own insulin was being produced on baricitinib: stimulated C-peptide was 0.65 vs 0.43 nmol/L per minute (2.0 vs 1.3 ng/mL per minute). The insulin dose was lower on average — 0.41 vs 0.52 U/kg per day, glucose fluctuated less, and glycated hemoglobin did not differ between the groups (Waibel M N Engl J Med 2023. PMID 38055252^[25]).

Six months after stopping, the difference was still present, but after a year it was no longer significant: the benefit probably requires continuous treatment (So M Diabetes Care 2026. PMID 42627334^[26]). For now these are trials, not treatment: the drug is not approved for diabetes. In a small trial in type 2 diabetes with kidney damage, baricitinib reduced albumin loss in the urine over 24 weeks by 41% compared with placebo, but a third of those on 4 mg developed anemia, and the drug has no such indication (Tuttle KR Nephrol Dial Transplant 2018. PMID 29481660^[27]).

What the trials showed: in brief

Not everything was confirmed: in lupus the first trial met its main goal (57% vs 46%), but the second did not repeat the result — 47% vs 46% (Morand EF Lancet 2023. PMID 36848918^[28]; Petri M Lancet 2023. PMID 36848919^[29]); in vitiligo, together with phototherapy, the prespecified goal was not met (Seneschal J JAMA Dermatol 2025. PMID 39841460^[30]).

Safety: what matters

How it is taken

• One tablet a day — 2 or 4 mg.
• Lab tests are done before starting and during treatment: the doctor decides which ones.
• In alopecia the result builds up over months and is assessed after about a year.
• Treatment is meant to be long-term: after stopping, hair usually falls out.

Bottom line

Baricitinib is the first pill approved in the US for severe alopecia areata in adults. Hair, eyebrows and eyelashes come back in many people, and in those who respond the result lasts for years with continued treatment. It is also used in rheumatoid arthritis and severe COVID, in the European Union and Japan in atopic dermatitis, and in type 1 diabetes it is still being studied. The decision about treatment is made together with a doctor after lab tests. Another JAK inhibitor for alopecia is covered in the article Alopecia areata and ritlecitinib; you can discuss your own treatment at a consultation.

This material is for information only and does not replace a consultation with a doctor. Baricitinib is a prescription drug; the decision on prescribing, dose and monitoring is made by a doctor based on examination results.