The compiled data revealed a link between the use of antihistamines and reduced production of male sexual hormones in the testicles, including inferior quality sperm and lower sperm count.
According to Medical News Today, a histamine is a molecule the body produces when the immune system is activated by a perceived threat. By sneezing, itching or making your eyes water, histamines attempt to remove the allergens from the body as a standard defense system.
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Previously, research has shown that histamines are connected to other bodily processes besides allergic reactions, including sleep-wake regulation, fertility and sexual behavior.
Antihistamines are commonly used to relieve the excessive symptoms of histamines (itching, sneezing) and other major allergic reactions, such as hives, hay fever, conjunctivitis or reactions to bee stings and insect bites. Different variations of allergy medications are available over-the-counter or with a prescription.
For their research, the scientists reviewed studies that specifically looked at the effects of antihistamines on animals – not humans. They say more research needs to be conducts on the effects of antihistamines on humans.
"More large-scale trials are needed to evaluate the possible negative effects of antihistamine on reproductive and sexual health," study author Dr. Carolina Mondillo told The Guardian.
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"This can then lead to developing novel treatments to relieve allergy symptoms without compromising fertility," she said, explaining that the data "indicates the crucial involvement of histamine in orchestrating testicular functions." But Mondillo also stressed that there is much more to learn "about the implicated mechanisms."
But this doesn’t mean all men who take allergy medicine are prone to have problems with infertility.
"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," Kevin McEleny, from the British Fertility Society told the Telegraph.
John Smith, the chief executive of the Proprietary Association of Great Britain who was not involved int the review, also echoed similar sentiments.
"People taking over-the-counter antihistamines should not be concerned by this research," he told the Guardian. Such medications, he said, are an "effective" and "appropriately safe" way to get allergy relief.
It’s also important to note that while the use of antihistamine allergy medication has increased rapidly in recent years, male infertility has also increased overall.
"The average sperm quality in the population has been reducing over the last few decades, so it is always important to consider that common – and increasingly used – medications may be partly responsible," Dr. Channa Jayasena, senior clinical lecturer at Imperial College London, told the Guardian.
She also cautioned against raising "alarm bells" about these common medications.
Up to 15 percent of couples struggles to conceive, according to the Mayo Clinic. And male infertility plays a role in up to half of these cases.
A study by researchers in Denmark in France published earlier this year suggested that ibuprofen (commonly sold under brand names Motrin or Advil) may also be linked to infertility in men. The study showed that within just two weeks, men given the maximum amount of ibuprofen experienced problems in certain testicular cells, hindering the production of testosterone.