Encyclopedia · drug with hair side effects
Methotrexate
A weekly immune-suppressing medicine that thins hair in a few percent of users, and is also used off-label for severe alopecia areata.
What it is
An antimetabolite that blocks folate metabolism, used at high doses in cancer and at low weekly doses in psoriasis and rheumatoid arthritis. It is prescription-only. Dermatologists also use it off-label for extensive alopecia areata, so it can both harm and, in autoimmune hair loss, help hair.
How it works
Blocking folate slows DNA synthesis in fast-dividing cells such as follicles, and dampens immune activity. High-dose chemotherapy is the classic cause of sudden anagen effluvium; which pattern low-dose use produces is not well characterised. Sinha 2020
What the studies show
- The US label reports alopecia in 1% to under 3% in one trial table, 0.5% in rheumatoid arthritis trials (n = 680), and 3% to 10% in psoriasis series at up to 25 mg/week. US label
- Case report: anagen effluvium after only two doses of 7.5 mg/week, described as idiosyncratic. Sinha 2020
- For alopecia areata, a meta-analysis of retrospective studies found reasonable effectiveness in severe cases, with adults responding better than children and many relapses on tapering. The data are low quality. Phan 2019
- A review of 13 series (226 people with alopecia totalis) found regrowth in 20% to 90%, relapse in 20% to 80% and adverse effects in 7% to 60%, so evidence is insufficient. Browne 2018
- A European expert consensus lists methotrexate among off-label options for systemic alopecia areata treatment; baricitinib and ritlecitinib are the approved ones. Rudnicka 2024
How it's used in studies
Dosing is weekly, not daily: 7.5-15 mg per week in rheumatoid arthritis trials and up to 25 mg per week in psoriasis series. Daily dosing by mistake has caused deaths. No supplement has been shown to prevent methotrexate hair loss.
Side effects and safety
- The boxed warning covers embryo-fetal toxicity including fetal death; it is contraindicated in pregnancy for non-cancer uses.
- It also warns of severe bone marrow, liver, lung, kidney and skin toxicity, hypersensitivity and dosing errors.
Bottom line
A few percent of users notice thinning, usually dose-related. If shedding appears, check iron and thyroid first (iron and ferritin, antithyroid drugs), since psoriasis and illness also shed hair. It is not a drug to start for hair reasons alone. Discuss with a doctor.
Studies 6
Methotrexate tablets prescribing information. DailyMed. Retrieved 2026-10-10
Result: Alopecia in 1% to under 3% in one table, 0.5% in rheumatoid arthritis trials and 3% to 10% in psoriasis series; boxed warning for embryo-fetal toxicity.
Read the study ↗Sinha. Anagen effluvium after methotrexate. 2020
Tested: methotrexate 7.5 mg/week
Result: Anagen effluvium after two doses, called idiosyncratic.
Read the study ↗Phan. Methotrexate for alopecia areata: SR and MA. 2019
Tested: methotrexate
Result: Reasonable effectiveness in severe alopecia areata; adults respond better than children; many relapses on tapering; low-quality data.
Read the study ↗Browne. Methotrexate for alopecia totalis: critically appraised topic. 2018
Tested: methotrexate
Result: Regrowth in 20% to 90%, relapse in 20% to 80%, adverse effects in 7% to 60%; evidence insufficient.
Read the study ↗Rudnicka L et al. European expert consensus statement on the systemic treatment of alopecia areata. J Eur Acad Dermatol Venereol. 2024
Tested: systemic treatments for alopecia areata
Result: Lists off-label glucocorticoids, methotrexate, cyclosporine and azathioprine alongside approved JAK inhibitors.
Read the study ↗Tosi A et al. Drug-induced hair loss and hair growth. Drug Saf. 1994
Tested: various drugs
Result: Hypertrichosis is a common effect of cyclosporin, minoxidil and diazoxide.
Read the study ↗Related
- AcitretinA prescription retinoid for severe psoriasis whose most common side effect is hair thinning, and which must never be used in pregnancy.
- BiotinA B vitamin that restores hair only in the rare people who are deficient, and that can scramble thyroid and heart blood tests at the doses sold for hair.
- ZincTrue zinc deficiency causes hair loss that zinc fixes, but zinc has not been shown to regrow hair in people who are not deficient, and too much causes copper deficiency.
- Iron and ferritinLow iron stores are common in people who shed hair, but no trial has shown that iron pills regrow hair, and nobody agrees on a hair-specific ferritin target.
- Folate (vitamin B9)A B vitamin that is sometimes low in people with hair loss, but not a hair-growth supplement if your levels are normal.
- Alopecia areataAn autoimmune condition where the immune system attacks growing hair follicles, causing round patches or total hair loss; three oral JAK inhibitors are approved for severe cases but hair usually goes again when treatment stops.