Infants Grow Excessive Body Hair in Outbreak of 'Werewolf Syndrome'

Mar. 15, 2025

Stock images of a child who has werewolf syndrome.Photo:Pedro Puente Hoyos/EPA-EFE/Shutterstock

Pedro Puente Hoyos/EPA-EFE/Shutterstock

Eleven babies in Europe have developed hypertrichosis — commonly known as “werewolf syndrome,” which is excessive hair growth over the entire body — after exposure to their caregivers’ topicalhair-regrowth medication.

The babies and toddlers were exposed to medication containing 5% of the hair-regrowth componentminoxidil, according to a report inEl Economista.The caregivers had been prescribed the medication for baldness, as well asalopecia areata, which theCleveland Clinicexplains is “an autoimmune disease that attacks your body’s hair follicles, causing patchy hair loss.”

Stock image of a child who developed werewolf syndrome.AP Photo/Sergio Ruiz

AP Photo/Sergio Ruiz

“Infant skin is functionally still developing, and the impaired barrier function of newborn skin makes it more susceptible to chemical irritation and local or systemic infections compared with adults,” theNational Library of Medicineexplains.

Another report from theNational Library of Medicineexplained further. “Very immature infants in the early neonatal period have a poorly developed epidermis, which is readily permeable to drugs. The main consequences of percutaneous absorption are hazardous. Topically applied agents are absorbed, causing toxic systemic effects that may result in illness.”

The PEOPLE Puzzler crossword is here! How quickly can you solve it? Play now!

Once exposure to minoxidil ceased, the children stopped growing excessive hair.

However, while “hypertrichosis is the most common” side effect from minoxidil exposure, theNational Library of Medicinenotes there are other risks, including “fluid retention, arrhythmia, electrocardiogram alterations and pericarditis.”

AsNewsweekreports, minoxidil packages in Europe will now have a warning label advising users to avoid touching young children after applying the medication.

Never miss a story — sign up forPEOPLE’s free daily newsletterto stay up-to-date on the best of what PEOPLE has to offer, from celebrity news to compelling human interest stories.

source: people.com