How a Woman’s Nut Allergy Was Triggered After Sex

Diagnostic Dilemma: A Woman's Nut Allergy Triggered After Sex

A 20-year-old woman in the United Kingdom recently presented with a perplexing case of severe allergic reactions after engaging in unprotected vaginal sex with her habitual male partner. Within moments of intercourse, she began to experience intense itching and swelling in her vulva and vagina. This was soon followed by a more serious reaction, including hives and widespread swelling (angioedema) across her body. As her symptoms progressed, she felt faint and struggled to breathe—an alarming presentation that led to her seeking urgent medical attention.

The Case: A Mystery Allergic Reaction

The patient had a known medical history of severe allergies to Brazil nuts, a particular type of tree nut. Despite being cautious about her allergies, she had no immediate explanation for what had triggered this latest reaction. Although her partner had consumed Brazil nuts two to three hours before their sexual encounter, he had carefully taken a bath, brushed his teeth, and thoroughly cleaned his fingernails in an effort to remove any trace of the allergens. Despite these precautions, she had an acute allergic response soon after intercourse.

Initial Management

Upon arriving at the hospital, the woman was administered 10 milligrams of cetirizine, an oral antihistamine commonly used to treat hives and mild allergic reactions. Within 45 minutes, her symptoms began to improve, although she felt fatigued the next day. She did not experience any further hives, dizziness, or shortness of breath, and her breathing returned to normal.

The Diagnostic Process: Could Semen Be the Culprit?

Given the patient’s history of Brazil nut allergies, doctors at the hospital suspected that the allergic reaction could have been triggered by the proteins from Brazil nuts being transferred through her partner's semen. In the past, there have been cases of allergic reactions linked to intimate contact, typically involving allergens transferred via kissing or direct skin contact. However, this was an entirely new and unusual scenario, as there had never been a documented case of an allergic reaction caused by vaginal intercourse.

To investigate further, the medical team conducted skin prick tests on the patient using two semen samples from her partner. One sample was collected when the man had not eaten Brazil nuts, while the other was obtained after he had consumed Brazil nuts about 2.5 hours prior. When the second sample was tested on the patient’s skin, a 0.28-inch (7-millimeter) welt appeared—an indicator that Brazil nut allergens were indeed present in the semen, and that they were likely responsible for triggering her severe allergic reaction.

Treatment and Long-Term Management

The woman’s symptoms improved significantly after the cetirizine treatment. Although she was tired the next day, her breathing returned to normal, and she no longer experienced dizziness or hives. As part of her follow-up care, the doctors advised her to carry antihistamines and an adrenaline pen (EpiPen) in case of future allergic reactions. Most importantly, they instructed her to avoid sexual intimacy with her partner if he had consumed Brazil nuts recently.

What Makes This Case Unique?

While it’s not uncommon for individuals with severe allergies to experience reactions following intimate contact, these reactions are usually due to the direct transfer of allergens via touch or kissing. In those cases, allergens present on a person’s hands, mouth, or lips are passed on to the allergic individual. This case, however, marks the first documented instance of a severe food allergic reaction triggered specifically by normal vaginal intercourse. Doctors concluded that the transfer of Brazil nut allergens through semen was a plausible cause of the woman’s reaction.

Key Takeaways

• Diagnosis: In this case, the woman’s history of Brazil nut allergies, combined with the timing of her symptoms and the presence of allergens in her partner’s semen, pointed to the nuts being the cause.
• Management: The patient was treated with cetirizine and advised to carry an EpiPen. She was also instructed to avoid intercourse with her partner if he had recently eaten Brazil nuts.
• Uniqueness: While there are cases of food allergies triggered by intimate contact, this case represents the first documented instance where vaginal intercourse resulted in a severe food allergy reaction due to allergens in semen.
• Implications: This case highlights the importance of understanding the full spectrum of allergic reactions, including how food allergens can be transferred in intimate settings, and the necessity of tailored precautions for individuals with known food allergies.

This case is a striking reminder that food allergens can be more pervasive than we might think, crossing boundaries like skin-to-skin contact or even semen, and can trigger severe reactions in unexpected contexts.