Babies develop 'werewolf syndrome' after parents use hair loss drug minoxidil: report

Minoxidil is used to treat hair fall and baldness. (Representational)

Eleven cases of "werewolf syndrome" or hypertrichosis have emerged among infants in Spain, linked to their caregiver’s use of over-the-counter hair-loss treatments containing minoxidil. The rare condition is characterised by excessive hair growth resembling fur.

The Navarra Pharmacovigilance Center recently reported that each affected infant's caregiver had used topical 5% minoxidil, a popular ingredient in products like Rogaine and Hims.

Investigators suspect that the drug was inadvertently absorbed by the babies either through skin contact or orally. “The condition receded completely when caregivers ceased using the treatment,” the report by El Economista noted.

The infants developed excessive hair growth on their back, legs, and face, in some cases giving them a striking resemblance to fictional characters such as Chewbacca from Star Wars. While fewer than 100 such cases have been documented globally since the Middle Ages, Spain has seen a sudden spate of cases since last year.

The phenomenon first gained widespread attention in 2023 when a breastfeeding infant developed body hair over two months. During a follow-up with the family, officials discovered that the father had been using 5% minoxidil for androgenic alopecia. Once he stopped the treatment, the child’s condition reversed.

Health experts have reiterated the dangers of minoxidil exposure to infants, with the European Pharmacovigilance Risk Assessment Committee issuing strong warnings. Hypertrichosis isn’t the only risk; ingestion of the drug can lead to severe complications. In one case, a French girl was hospitalised with tachycardia and hypotension after swallowing a teaspoon of minoxidil, according to Reuters.

Spain has dealt with similar incidents in the past. In 2017, at least 17 children developed hypertrichosis after minoxidil was mistakenly mixed into acid reflux medication. Elsewhere, in Malaysia, a 2-year-old girl with congenital hypertrichosis was affectionately called a “child from heaven” by local monarchs, highlighting a stark difference between genetic and environmental causes of the condition.

While hypertrichosis is rare and often reversible in such cases, its sudden occurrence has spotlighted the need for awareness about the risks of household medications. Experts urge caution, especially for parents using products that might unintentionally expose their infants to harmful substances.