Taking hayfever tablets could put men at higher risk of infertility, a study claims.
Scientists said the findings suggest men should limit the use of over-the-counter antihistamines when trying for a family.
Around one in six couples struggle to conceive - with male infertility linked to at least a third of cases.
Millions of Britons take antihistamine tablets, to treat symptoms of allergies such as hayfever.
Up to one third of adults are estimated to suffer such allergeies, which can cause a runny or blocked nose, itchy eyes, wheezing, sneezing or skin rashes.
The drugs work by controlling levels of histamine, a molecule produced by the immune system in response to a potential threat.
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Argentinian scientists reviewed more than 60 studies on how the drugs affects male fertility, mostly using animal trials.
They concluded hayfever tablets are likely to affect the production of male sexual hormones in the testicles, which can lead to lower quality sperm, as well as a reduced sperm count.
The researchers from the Institute of Biology and Experimental Medicine, in Argentina, said men trying for families should be cautioned against antihistamine overuse, while larger studies were carried out.
Hay fever factfile
Dr Carolina Mondillo, one of the study’s authors said. “More large-scale trials are needed to evaluate the possible negative effects of antihistamine on reproductive and sexual health.
“This can then lead to developing novel treatments to relieve allergy symptoms without compromising fertility”.
It comes amid a rise in allergies across the industrialised world, leading to growing use of drugs such as antihistamines.
John Smith, chief executive of the Proprietary Association of Great Britain, said: “The researchers’ key conclusion is that further human clinical studies are needed before any clear links between antihistamines and male fertility can be established.
“People taking over-the-counter antihistamines should not be concerned by this research,” he said.
“Antihistamines are an effective and appropriately safe way to provide relief from symptoms of allergies if used in accordance with the clear on-pack instructions and the patient information leaflet inside,” he said.
Kevin McEleny, from the British Fertility Society said “This review article outlines the possible role of histamine in the testicle. It doesn’t address the impact of antihistamines on testicular health. There is no evidence here that men who take antihistamines for a medical condition should have any concern.”
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