MEDICINES
Medicines that change hair colour, curl or lashes
In short
Some medicines darken white hair, curl it or lengthen lashes. Changes show in new hair and usually fade. This is not medical advice, just handy to know. Talk to a doctor if you want to explore this option further.
Do this
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1
Tell your doctor if your hair changes after a new medicine.
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2
Never stop or change a prescribed drug on your own because of your hair.
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3
Most texture and lash changes fade after stopping, but a few last.
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4
Check lash serum labels for bimatoprost, latanoprost, travoprost or names containing 'prost'.
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5
Skip serums with no full ingredient list or drug-like growth promises.
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6
See a doctor if your eyes turn red or sore on a lash product.
The numbers behind it
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13 of 14
People in a lung cancer case series whose white hair darkened on anti-PD-1 or anti-PD-L1 immunotherapy. It was a diffuse darkening.
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17 of 21
Cases with a known outcome in a 2022 review where a medicine's hair texture change reversed, from 3 weeks to 5 years after stopping.
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78% vs 18%
Share with fuller lashes after 16 weeks of bimatoprost 0.03% versus vehicle. Lashes also grew longer, thicker and darker (278 people).
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4 of 64
Lash serums bought online in Japan that held the prescription drug bimatoprost. Three of the four did not list it on the pack.
For your hair
White or gray hair
Anti-PD-1 immunotherapy and cancer drugs such as imatinib are linked to darker hair. They are cancer drugs, not hair treatments.
Straight hair
Chemotherapy regrowth, retinoids, valproate and erlotinib are linked to new waves or curls in case reports.
Curly hair
Straightening is the rarest change: a few interferon-alfa case reports, and lithium users who noticed hair losing curl or wave.
Short or light lashes
Prostaglandin eye drops lengthen, thicken and darken lashes. The same drug is in glaucoma drops and in some lash serums.
Myths to ignore
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Myth A cosmetic lash serum holds only cosmetic ingredients.
Truth Of 64 serums bought online in Japan, 4 held bimatoprost (3 without saying so) and 8 held other prostaglandin analogues that are not used as medicines.
Rahman 2022 ↗ -
Myth Hair that changes on a medicine is damaged for good.
Truth Most reported changes reversed after stopping (17 of 21 with a known outcome). A few, linked to retinoids, cancer drugs and antiretroviral drugs, stayed.
Phong 2022 ↗ -
Myth Chemo curls are a proven result with known rates.
Truth Curling is the most reported change, but reviews cannot give a rate. The one measured study found regrown hair thinner after chemotherapy.
Lindner 2012 ↗ -
Myth Cancer immunotherapy is a fix for gray hair.
Truth Darkening was a side effect of serious cancer drugs. In 29 people it was clear with immunotherapy but not with chemotherapy alone.
Jiang 2026 ↗
Go deeper
- Drug-induced hair changesMedicines can thin hair, regrow it curly, darken or whiten it, or lengthen lashes; this table sorts the best-known links by how strong the evidence is.
- Gray hair and premature grayingGraying is mostly genetic, but single-hair mapping shows some gray hairs can regain colour, and the famous stress-causes-gray mechanism was shown in mice.
- Beards and eyebrowsBeard preferences depend on context and what is fashionable, even beards beat patchy ones, and cosmetic options such as minoxidil for beards and microblading for brows rest on small studies.
- Hair shaft disordersStructural defects in the hair strand itself, either inherited or caused by repeated stress, that make hair break easily and can look like thinning even though the follicle is healthy.
All studies in this guide (17)
Rivera N et al. Hair repigmentation during immunotherapy treatment with an anti-programmed cell death 1 and anti-programmed cell death ligand 1 agent for lung cancer. JAMA Dermatol. 2017
Result: Diffuse darkening of hair in 13 of 14; 13 had at least stable disease.
Read the study ↗Jiang S et al. The impact of immunotherapy on hair repigmentation in patients with thoracic tumors: a clinical observation based on trichoscopy. Thorac Cancer. 2026
Tested: immune checkpoint inhibitor immunotherapy versus chemotherapy alone; hair darkness measured from scalp images before and after treatment
Result: Hair grew darker in the immunotherapy group (grayscale change 23.5 versus 4.32 with chemotherapy alone, p = 0.0065), while the chemotherapy-only group did not change significantly.
Read the study ↗Yale K et al. Medication-induced repigmentation of gray hair: a systematic review. Skin Appendage Disord. 2020
Result: Many drugs and some B vitamins were reported to repigment gray hair, mostly as incidental, low-quality reports.
Read the study ↗Phong C et al. Systemic medications associated with hair texture changes. J Drugs Dermatol. 2022
Result: Across 31 papers, texture changes occurred with chemotherapy drugs, antiepileptics, retinoids and antiretrovirals; new or stronger curling was most common, starting 4.5-17 months in, and usually reversible.
Read the study ↗Lindner J et al. Hair shaft abnormalities after chemotherapy and tamoxifen therapy in patients with breast cancer evaluated by optical coherence tomography. Br J Dermatol. 2012
Tested: hair shaft measured by optical coherence tomography before and after treatment
Result: Hair that regrew after chemotherapy had a significantly smaller cross-section than before, and its shape changed at the back of the head. Tamoxifen caused no change.
Read the study ↗Clarke JT et al. Acquired kinking of the hair caused by acitretin. J Drugs Dermatol. 2007
Tested: acitretin
Result: A woman's hair became kinked about 6 months after starting acitretin and stayed that way even when the dose was cut. The authors suggest retinoids may affect the inner root sheath that shapes the hair.
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 ↗Seckin. Repigmentation and curling of hair after acitretin. 2009
Tested: acitretin
Result: White hair darkened and became curly.
Read the study ↗Caneppele S et al. Sodium valproate-induced kinky hair. Ann Dermatol Venereol. 2001
Tested: sodium valproate
Result: A girl on valproate developed kinky, dry, lustreless hair. The authors note five earlier valproate cases with hair shaft changes.
Read the study ↗Zheng H et al. Trichomegaly and scalp hair changes following treatment with erlotinib. Exp Ther Med. 2016
Result: Curly, long, brittle eyelashes and altered scalp hair; all gradually resolved after the drug was withdrawn.
Read the study ↗Bessis D et al. Straight hair associated with interferon-alfa plus ribavirin in hepatitis C infection. Br J Dermatol. 2002
Tested: interferon-alfa plus ribavirin
Result: A case report of straight hair appearing during interferon-alfa plus ribavirin treatment for hepatitis C.
Read the study ↗McCreadie. Lithium and hair texture. 1985
Result: Patients whose hair lost curl or wave had higher hair lithium concentrations.
Read the study ↗Hutchison DM et al. Eyelash trichomegaly: a systematic review of acquired and congenital aetiologies of lengthened lashes. J Eur Acad Dermatol Venereol. 2022
Result: Medicines linked to longer eyelashes were prostaglandin analogues (bimatoprost, latanoprost, travoprost), EGFR inhibitors (cetuximab, erlotinib, panitumumab), interferon-alpha and calcineurin inhibitors (tacrolimus, cyclosporine). The most common cause was topical bimatoprost.
Read the study ↗Smith S et al. Eyelash growth in subjects treated with bimatoprost: a multicenter, randomized, double-masked, vehicle-controlled, parallel-group study. J Am Acad Dermatol. 2012
Tested: bimatoprost 0.03% vs vehicle on the upper lash line
Result: At least a 1-grade improvement in lash prominence in 78.1% vs 18.4% on vehicle; length, thickness and darkness all improved.
Read the study ↗Johnstone MA. Hypertrichosis and increased pigmentation of eyelashes and adjacent hair in the region of the ipsilateral eyelids of patients treated with unilateral topical latanoprost. Am J Ophthalmol. 1997
Tested: latanoprost eye drops
Result: The treated side grew more, longer, thicker, curlier and darker lashes.
Read the study ↗Johnstone MA, Albert DM. Prostaglandin-induced hair growth. Surv Ophthalmol. 2002
Result: In five patients, 2 to 17 days of prostaglandin eye drops produced eyelash changes comparable to long-term treatment.
Read the study ↗Rahman MS et al. Screening and quantification of undeclared PGF2-alpha analogs in eyelash-enhancing cosmetic serums using LC-MS/MS. J Pharm Biomed Anal. 2022
Tested: laboratory analysis
Result: 4 of 64 serums contained bimatoprost (3 not declared on the label) and 8 contained other prostaglandin analogues.
Read the study ↗