Dangerous Liaison: Woman Suffers Anaphylactic Reaction After Vaginal Sex

A 20-year-old woman in the UK with a severe tree nut allergy had unprotected vaginal sex with her habitual partner. Shortly afterward, her vulva and vagina began itching and swelling, urticaria (hives) spread across her body, and she began to feel faint and short of breath, signs of an anaphylactic reation.

Anaphylaxis is a severe, life-threatening reaction to a food, drug, insect venom or substance, like latex.

She visited the hospital, where she was treated with cetirizine, an oral antihistamine often used to treat hives, although it was unclear what had triggered her reaction. After 45 minutes, her symptoms eased. Although she felt tired the next day, her other symptoms had resolved.

Her partner had eaten Brazil nuts about two or three hours before intercourse, but he had been careful to brush his teeth and clean his fingernails prior.

Skin prick tests were conducted using various semen samples from her partner, one sample taken when her partner had not eaten Brazil nuts prior, and one where he had consumed the nuts 2.5 hours before.

In the latter test, the woman developed a welt 0.28 inches long, indicative that she was sensitive to the sample taken after nuts were consumed by the man.

The doctors instructed her to keep antihistamines on hand as well as an epinephrine auto-injector. They suggested she abstain from sexual intimacy with her partner after he had eaten Brazil nuts.

There are other documented cases of individuals suffering allergic reactions after intimacy, but they have generally involved the transfer of allergens from the mouth or touch.

“To our knowledge this is the first case of a severe food allergic reaction transferred by normal vaginal intercourse,” doctors at the hospital wrote in a report.

While this report shows yet another unexpected avenue for the transmission of allergens, we are unsure why the woman was treated at the hospital with cetirizine, which doctors now advise against.

Epinephrine is the only known drug that can halt and reverse the symptoms of anaphylaxis. As Harvard Medical School states:

There is no substitute for epinephrine, which is the only first-line treatment for anaphylaxis. Neither antihistamines nor glucocorticoids work as quickly as epinephrine, and neither can effectively treat the severe symptoms associated with anaphylaxis.

However, antihistamines such as diphenhydramine (Benadryl) or cetirizine (Zyrtec), glucocorticoids like prednisone, or a combination, may be used in addition to epinephrine in some cases of anaphylaxis, after epinephrine is administered.