A commonly used over-the-counter hair loss treatment has been linked to excessive hair growth in infants and serious eye disorders in adults, raising fresh concerns about its widespread and largely unregulated use, according to a new global safety study.
Minoxidil, originally developed as a medication for high blood pressure, was later repurposed as a topical treatment for hair loss after doctors observed hair regrowth as a side effect. Today, it is widely sold without prescription in sprays and foams to treat androgenetic alopecia, or male and female pattern baldness.
The study, published in Archives of Dermatological Research, analysed adverse drug reaction reports submitted to the World Health Organization’s global safety database, VigiBase, up to March 2025. Researchers from the Indian Pharmacopoeia Commission, under the Ministry of Health and Family Welfare, in collaboration with the All India Institute of Medical Sciences, examined both global and India-specific data to assess safety risks linked to minoxidil use.
Infants developing abnormal hair growth
The analysis identified 2,664 global reports of suspected infantile hypertrichosis — a condition marked by excessive and abnormal hair growth, sometimes described as fur-like — associated with minoxidil exposure. Of these, 45 cases involved children under the age of two.
According to the study, 22.2% of the cases were linked to maternal exposure during pregnancy or breastfeeding, 44.4% followed accidental exposure, and the remaining 33.3% had an unknown source. No cases were reported from India, though researchers cautioned that under-reporting is likely given the drug’s widespread availability.
Infants are particularly vulnerable due to their thin skin and higher absorption capacity. “There is potential for a much larger number of cases which haven’t been identified, owing to low reporting in the region,” the authors noted, calling the findings “concerning” in light of minoxidil’s over-the-counter status.
How infants are exposed
Researchers said infants can be exposed to minoxidil through several routes, including skin-to-skin contact or accidental ingestion via breastmilk. When adults apply minoxidil to the scalp, the drug can transfer to babies during holding, cuddling or feeding.
Because minoxidil works by widening blood vessels and stimulating hair follicles through potassium channels, infants may develop an exaggerated response, resulting in hair growth across large areas of the body rather than just the scalp.
Despite being contraindicated for use during pregnancy and breastfeeding, the study suggests that a lack of awareness and easy access may be contributing to continued use among these populations.
Serious eye disorders in adults
In addition to risks for infants, the study identified 1,669 global cases of eye disorders associated with minoxidil use, including 25 reports from India. Symptoms ranged from eyelid swelling and eye irritation to blurred vision and central serous chorioretinopathy, a condition in which fluid accumulates beneath the retina.
Of the Indian reports, nine were classified as serious, with four confirmed after removing duplicate records. These included three cases of central serous chorioretinopathy and one case of retinal artery occlusion, a blockage of blood flow to the retina.
Why minoxidil affects the eyes
The researchers explained that minoxidil is absorbed into the bloodstream even when applied topically. Its vasodilatory effect can increase blood vessel permeability in the choroid, the layer of blood vessels behind the retina, leading to fluid leakage beneath the retina and subsequent vision problems.
“While minoxidil has proven efficacy in managing androgenetic alopecia in adults, its widespread and often unregulated availability raises significant safety concerns, particularly in vulnerable populations such as infants and young children,” the authors said.
Call for tighter regulation
The study’s authors called for clearer warning labels, stricter regulation of over-the-counter sales, and improved counselling by healthcare professionals. They urged regulators to ensure serious eye-related side effects are more prominently mentioned in patient information leaflets and to address misleading marketing claims that encourage unsupervised use.
“There is a pressing need for enhanced patient counselling and caregiver education regarding the potential risks of minoxidil, especially when used in households with children,” the researchers said, adding that healthcare professionals should consider minoxidil as a possible cause when patients present with unexplained eye symptoms.
The findings aim to strengthen drug safety awareness and reporting practices, particularly in countries such as India, where minoxidil use remains widespread and largely unmonitored.
