Common allergy drugs have been linked to fertility problems in men.
Antihistamines are often used to relieve symptoms of allergies, such as hay fever, hives, conjunctivitis and reactions to insect bites or stings, and are available either over-the-counter or on prescription.
An Argentine study found these commonly-taken drugs could have negative long-term side effects for male fertility.
The review, which is published in the journal Reproduction, found a number of studies reported adverse effects of antihistamine on normal testicular function.
They discovered antihistamines were likely to affect the production of male sexual hormones in the testicles, which could lead to altered morphology and decreased motility of sperm, as well as a lower sperm count.
The researchers, who analysed a number of animal studies, said further research was needed as human studies were still very limited, but they cautioned against antihistamine overuse.
The rise in allergies in the industrialised world has led to an increased use of drugs such as antihistamines.
Histamine is a molecule produced by the body in response to an allergy.