The problem might sound rare, but as many as one in ten women may suffer from it. The reactions may be mild (irritation, itcing) but can be so severe as to cause a life-threatening allergic reaction called anaphylactic shock. It has also been shown to spark asthma attacks.
Nevertheless, Dr Michael Carroll, a lecturer in reproductive science at Manchester Metropolitan University, says his unpublished research indicates that up to 12 percent of women may have the condition. He says it appears underdiagnosed, partly because those affected are too embarrassed to see a GP.
He says doctors often misdiagnose the symptoms because of their similarity with other conditions such as dermatitis and some sexually transmitted diseases. Women aged 20 to 30 are thought to be worst affected, displaying reactions immediately, or up to an hour, after sex. Those with the allergy react adversely to all men’s semen.
Australian scientists believe this sensitivity could be a factor in another common and often debilitating condition – endometriosis, which causes painful or heavy periods.
Endometriosis is caused by the endometrial cells lining the womb migrating to the ovaries, the lining of the pelvis behind the uterus and the top of the vagina. It is also linked to infertility, with up to half of infertile women having the condition, says Endometriosis UK, adding that the cause is unknown and has no cure.
It is not only women who can suffer. In rare cases, men can be allergic to their own semen. Symptoms include a flu-like illness, with pain, redness and discomfort affecting the head, eyes, nose, throat and muscles, extreme fatigue and difficulty concentrating.
One case, reported in March in The Journal Of Sexual Medicine, involved a Chinese man whose skin broke out in rashes when exposed to his semen. Doctors at the Peking Union Medical College Hospital could identify no cause.
Research four years ago, by Dutch investigators in the same journal, identified 45 men with the problem. The symptoms occurred only after ejaculation, indicating the men were protected so long as the fluid remained in their testes.
Doctors are still developing ways to help women. Korean doctors reported in 2011 that they had helped a 33-year-old woman with severe allergic reactions to semen, including breathing trouble, to become pregnant by giving her antihistamine tablets to take one hour before making love.
Doctors at St Mary’s Hospital and the Department of Immunology at Central Manchester University Hospital, meanwhile, reported in the journal Human Fertility in 2013 that women with a high risk of anaphylactic shock from the allergy can be made pregnant by removing their partner’s sperm from the fluid and then implanting it.
Dr Michael Carroll, the reproductive scientist who led that study, says he has since been contacted by women all over the world with the problem.