Allergies during sex: Sex, allergic shock, death: How this rare case can occur

In 2006, a 38-year-old woman in Spain had a very unpleasant sexual experience. After having sex with her husband, her face swelled up and turned bright red. She also developed severe breathing problems. Her symptoms, which suggested an allergic reaction, began immediately after her husband ejaculated. The problem had not occurred on previous occasions when the couple had used condoms. However, because the woman wanted to become pregnant, the couple had not used contraception this time.

A few hours later, the affected woman sought medical help in the hospital. The doctors quickly found the cause of her symptoms. Using a prick test, they proved that she was allergic to her husband’s semen. This is very rare – there are only around 100 case reports in the scientific literature, and in none of them did the sexual act lead directly to the death of the affected person. But that does not mean that every allergic reaction during sex ends well.

This is shown by a report from Canada published in 2021, which describes how a young man lost his life as a result of fellatio. He met his newest partner on a dating app and they soon met for a date. What they didn’t know was that the first had a severe peanut allergy and the second had eaten peanut butter shortly before the date. While the second man performed oral sex on the allergy sufferer, he developed breathing problems. As an asthmatic, he had a bronchodilator with him, which he used immediately. However, a little later he collapsed and lost consciousness. An emergency team gave him artificial respiration and resuscitated him after his heart stopped. However, he died the next day as a result of the incident.

It was already known that passionate kisses can be dangerous for people with peanut allergies. Symptoms have been shown to occur up to six hours after a partner has a nutty snack. One study documented severe allergy symptoms two hours after a meal – even though the person had thoroughly brushed their teeth and rinsed their mouth in between. In the case from Canada, the two men had not kissed at all during their entire meeting. Just the contact of one person’s peanut-contaminated mouth with the other’s glans was enough to trigger the fatal reaction.

Allergens can also accumulate in the ejaculate, as a case from Spain documented in 2019 shows. A 31-year-old woman was hospitalized after developing hives all over her body. She also vomited several times and complained of shortness of breath. Shortly before, she had had unprotected oral and vaginal intercourse. She had never had such a reaction to sperm in the past; she was only unable to tolerate antibiotics from the penicillin group. Because of an infection, her partner took one. Because the doctors couldn’t find any other allergies, they concluded that traces of the active ingredient had gotten into the semen and caused the symptoms. The patient was given medication and completely recovered within a week.

All of these examples show that the exchange of bodily fluids poses more dangers for some of us than for others. People with severe food or drug allergies must therefore ensure that allergens do not enter their own body indirectly through their partner when making love. A condom can prevent this – and therefore not only protects against sexually transmitted infectious diseases, but also against potentially life-threatening immune reactions.

Incidentally, the medical team was able to fulfill the patient’s wish to have children despite her allergy to semen. To do this, they purified their partner’s ejaculate and isolated his sperm. They used these to successfully perform artificial insemination on the woman, which resulted in the birth of a healthy baby. However, the case report does not reveal whether the child inherited his mother’s allergy.

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