Eleven cases of “werewolf syndrome” in babies across Europe have been linked to their parents’ use of minoxidil, a hair-loss treatment, according to a report by the Pharmacovigilance Centre of Navarre (CFN) in Spain.
Hypertrichosis, or “werewolf syndrome,” is a rare condition characterized by excessive hair growth in areas other than the scalp. This unusual hair growth may cover the entire face and body or appear in smaller patches, as described by the US National Institute of Health (NIH).
The CFN report highlighted a connection between cases of hypertrichosis in infants and their caregivers’ use of minoxidil, a medication commonly used to stimulate hair growth and slow balding. Minoxidil is typically applied topically as a scalp solution or taken orally.
The investigation began when a baby in Spain exhibited abnormal hair growth on the back, legs, and thighs over two months. The baby’s father, who was using a 5% minoxidil solution for his baldness and had been on extended leave to care for his child, was found to be the source of the exposure. After the father discontinued the medication, the baby’s symptoms completely regressed.
Following this case, the CFN analyzed data from the Spanish Pharmacovigilance System and the European Medicines Agency’s (EMA) EudraVigilance databases. Their review identified similar incidents across Europe, all involving babies with hypertrichosis whose caregivers were using topical minoxidil.
The report proposed two potential pathways for the transmission of minoxidil to infants: direct skin contact or accidental ingestion. Babies’ thinner and more sensitive skin makes them particularly susceptible to absorbing topical medications.
The findings underscore the importance of caution when using medications like minoxidil, particularly around young children, to prevent unintended exposure.
