Encyclopedia · drug with hair side effects
Isotretinoin
A prescription acne drug that causes shedding in a few percent of users and, far more seriously, severe birth defects.
What it is
An oral vitamin A relative for severe, scarring or treatment-resistant acne. The US label dose is 0.5 to 1 mg/kg/day for 15 to 20 weeks, up to 2 mg/kg/day for very severe disease. US label It is prescription-only everywhere: in the US only through the iPLEDGE program, in the UK within specialist teams under a Pregnancy Prevention Programme. MHRA
How it works
Retinoids shrink oil glands and dry the skin. Hair loss is described as telogen effluvium, with follicles pushed into rest and shedding showing about 2 to 4 months later. Tosi 1994 Why texture or curl would change is unknown.
What the studies show
- A review of 22 studies found hair loss in 3.2% (18 of 565) on under 0.5 mg/kg/day versus 5.7% (192 of 3,375) at 0.5 mg/kg/day or more. No statistics were possible. Lytvyn 2022
- A Cochrane review of 31 trials (3,836 people) found hair loss among the less serious side effects, with low-quality evidence. Costa 2018
- In 124 courses of 1 mg/kg/day for 4 months, hair loss affected a small percentage and rarely lasted across visits. Hull 2000
- In 30 people on 0.5-1.0 mg/kg/day for 4 to 7 months, trichoscopy showed lower hair count, density and anagen proportion. Kmiec 2013
- At 0.5 mg/kg/day for 3 months, differences were not significant. Islamoglu 2019
- In a chart review of 6,330 hair-loss patients, 48 had taken isotretinoin; the 19 who lost hair had higher cumulative doses and longer treatment. Tran 2022
- In 60 patients on 0.5 mg/kg/day, adding 10 mg/day biotin for 4 months was linked to a higher anagen ratio (p = 0.034) and lower telogen ratio (p = 0.003). It was not blinded and no placebo was used. Aksac 2021 Biotin at that dose can distort blood tests; see biotin.
- Texture: a woman's hair became markedly curlier during a year of treatment for systemic sclerosis. This is case-report level, with no incidence figure. Bunker 1990
The US label lists alopecia, which in some cases persisted, without a percentage. Shedding usually recovers after stopping but is not guaranteed.
How it's used in studies
Hair studies used 0.5 mg/kg/day, 0.5-1.0 mg/kg/day for 4 to 7 months, or 1 mg/kg/day for 4 months.
Side effects and safety
- Pregnancy is the headline risk. The US boxed warning says the drug can cause life-threatening birth defects and is contraindicated in pregnancy. US label
- The US iPLEDGE rules were changed by the FDA in February 2026, with implementation delayed to 15 November 2026. Check the FDA page for current rules. FDA
- In a 2025 US claims study of women aged 14 to 45, pregnancy rates on isotretinoin were 15.7 and 3.3 per 1,000 person-years in two databases, versus 40.1 and 24.0 on topical retinoids, so exposure in pregnancy still happens. Zhu 2025
- The label advises against vitamin A supplements during treatment; see hair supplement blends.
- Dry skin, lips and eyes, joint pain and headaches are common; serious reactions include pancreatitis, seizures and mental-health problems.
Bottom line
Expect a small chance, a few percent in pooled reports, of diffuse shedding, more plausible at higher dose and longer courses and usually reversible. For severe or scarring acne this is rarely a reason to avoid the drug. If shedding starts, check iron (iron and ferritin), thyroid and recent illness, and do not add vitamin A. Anyone who can become pregnant must understand the pregnancy-prevention rules before the first dose. Discuss with a doctor.
Fun facts
- A 1990 case report described markedly curlier hair on isotretinoin. Drug-induced texture change also appears in case reports for acitretin and lithium. Bunker 1990
Studies 12
Lytvyn. Frequency of isotretinoin-induced hair loss <0.5 vs >=0.5 mg/kg/d. 2022
Tested: isotretinoin below vs at or above 0.5 mg/kg/day
Result: Hair loss 3.2% (18/565) at the lower dose vs 5.7% (192/3,375) at the higher dose; no inferential statistics.
Read the study ↗Costa. Oral isotretinoin for acne (Cochrane). 2018
Tested: oral isotretinoin
Result: Less serious adverse effects including hair loss occurred; heterogeneity precluded pooling; low-quality evidence.
Read the study ↗Hull. Isotretinoin use in acne: prospective evaluation of adverse events. 2000
Tested: isotretinoin 1 mg/kg/day
Result: Hair loss in a small percentage and rarely on more than one visit; dry lips in most, dry eyes in 40%.
Read the study ↗Kmiec. Biophysical skin parameters and hair growth in acne treated with isotretinoin. 2013
Tested: 0.5-1.0 mg/kg/day isotretinoin
Result: Lower total hair count, density and anagen proportion, read as telogen effluvium.
Read the study ↗İslamoğlu ZGK et al. Effects of isotretinoin on the hair cycle. 2019
Tested: 0.5 mg/kg/day isotretinoin
Result: TrichoScan differences before and after were not statistically significant.
Read the study ↗Aksac SE et al. Evaluation of biophysical skin parameters and hair changes in patients with acne vulgaris treated with isotretinoin, and the effect of biotin use on these parameters. 2021
Tested: 0.5 mg/kg/day isotretinoin with or without biotin 10 mg/day
Result: Biotin group had a higher anagen ratio (p=0.034) and lower telogen ratio (p=0.003); not described as blinded or placebo-controlled.
Read the study ↗Show 6 more studies
Tran. Characteristics of patients with hair loss after isotretinoin. 2022
Result: The 19 who lost hair had older age, higher cumulative doses and longer treatment than isotretinoin patients without hair loss.
Read the study ↗Bunker CB et al. Isotretinoin and curly hair. 1990
Tested: isotretinoin
Result: Hair became markedly more curly during treatment.
Read the study ↗Isotretinoin capsules prescribing information. DailyMed. Retrieved 2026-10-10
Result: Label dose 0.5 to 1 mg/kg/day for 15 to 20 weeks; boxed warning for life-threatening birth defects; alopecia, which in some cases persisted, is listed.
Read the study ↗US FDA. iPLEDGE Risk Evaluation and Mitigation Strategy (REMS). Retrieved 2026-10-10
Result: FDA page on the iPLEDGE isotretinoin risk program, including the February 2026 approved changes with implementation delayed to 15 November 2026.
Read the study ↗Zhu. Isotretinoin REMS and pregnancy incidence. 2025
Result: Pregnancy rates 15.7 and 3.3 per 1,000 person-years on isotretinoin vs 40.1 and 24.0 on topical retinoids.
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.
- 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.
- Hair supplement blends (Nutrafol, Viviscal and similar)Branded multi-ingredient hair vitamins that beat placebo in small, mostly company-linked trials.
- Antithyroid drugs (carbimazole, methimazole, propylthiouracil)Medicines for an overactive thyroid; shedding on them can come from the thyroid disease, an over-treated thyroid, or the drug, which is hard to separate.
- Vitamin AToo much preformed vitamin A can make hair fall out, so extra vitamin A in a hair supplement is more likely to harm than help.
- LithiumA mood-stabilising medicine whose label lists hair thinning, with figures ranging from no excess in trials to about 1 in 5 in older surveys.
- Telogen effluviumA temporary burst of diffuse shedding that starts 2 to 3 months after a physical or emotional shock and usually settles within 6 months once the trigger is gone; it does not cause bald patches.