The popular painkiller ibuprofen can damage men's ability to have children, according to a new joint Danish and French study.
The scientists found that when taken regularly for up to six weeks the drug can cause damage to the male hormone in the testicals, meaning they are less likely to be able to conceive.
The doctors in Copenhagen also witnessed other health problems such as erectile dysfunction, fatigue and muscle wastage.
Some of the conditions would normally be associated with older men and smokers, but the group taking part in the study were aged 18 to 35. They took 600mg of ibuprofen twice a day.
The researchers said the disorder was mild and short-lived but there was risk it could become permanent in long-term users.
"In general, I think it's bad thing when you can buy something without a prescription that can harm you," said student Niels Justesen. "If it's accurate that it can damage men's hormonal balance it's bad, and maybe you shouldn't be able to buy it without a prescription, but by prescription only, if you ask me." This latest development comes after warnings from other researchers that ibuprofen can cause medical complications for pregnant women and their babies such as raising the risk of miscarriage.