At least 17 children, some of them babies, have developed “werewolf syndrome” after a serious pharmaceutical mix-up, according to the Spanish department of health.

The children have reportedly grown abnormal extra hair on their heads, cheeks, arms and legs after being given medicine for gastric reflux that turned out to contain a drug used to treat alopecia, or baldness, health regulators said.

The medicine had been distributed by FarmaQuímica Sur, a pharmaceutical company in the Malaga region of Spain. The product was withdrawn soon after the first cases were reported, in July.

Yesterday the health ministry said an “internal error” meant a batch of minoxidil, used to stimulate hair growth, had been incorrectly labelled as omeprazole, which is used to treat gastroesophageal reflux disease.

One mother told the Spanish newspaper El Mundo that she panicked when her 22-month-old daughter “began to grow hair on her face” after taking a syrup that had been prescribed for her stomach complaint.

Another child was just six months old when thick hair began to grow all over his body; his mother told the newspaper El País that he had developed “adult’s eyebrows”. “It was very scary, because we didn’t know what was happening to him,” the mother, Angela Selles, said. The baby had been taking the same syrup.

‘Werewolf syndrome’: hypertrichosis is a rare condition that causes thick hair to grow over the body, often on the face, as in the case of this 13-year-old Indian schoolboy, Lalit Patidar. Photograph: Shams Qari/Barcroft via Getty

The minoxidil created an appearance of “werewolf syndrome”, or hypertrichosis, a rare condition that causes thick hair to grow over the body, often on the face and in other unusual places.

Farma-Química Sur has been banned from manufacturing or distributing any medication until the incident has been resolved and all affected omeprazole has been recalled, according to El País.

Parents have been told that the children’s symptoms should improve within weeks, as their excess hair will fall out now they have stopped taking the medicine. – Agencies