Sci will be honest: I hate Brazil nuts. I have no idea why anyone eats them, they always taste all sour and gritty and WEIRD. The taste just kind of lingers in your teeth. But what if it didn’t just linger in your teeth? What if it lingered in your…semen?
Ah, Sci, you say. You’re always all about the semen.
Bansal et al. “Dangerous Liason: Sexually transmitted allergic reaction to Brazil Nuts” Journal of Investigative Allergy and Clinical Immunology, 2007.
Semen allergy is actually more common than you might think. Many people can show allergy to some of the components of semen, which can make sex both seriously uncomfortable and really, really obvious. Not to mention problems if you’re trying to get pregnant! But that’s an allergy to semen itself. What about an allergen, an allergic reaction TRANSMITTED through the semen?
That’s what apparently happened here. 20 year old woman with a boyfriend. Woman had a really bad allergy specifically to Brazil nuts. While she gave them up after getting diagnosed, her boyfriend apparently had a real nut fetish and couldn’t stay away from the mixed. In an effort to protect her, he carefully bathed, brushed his teeth (there have actually been deaths in those with nut allergies when they get kissed after someone else eats nuts), and even cleaned out his fingernails before sex. All in vain. Immediately after sex she began to suffer itching and swelling of the vag, got short of breath, and felt faint. A little bit of antihistamine helped to solve the problem, but it was bad enough that she ended up going to the doctor.
When the doctors had ascertained that the boyfriend had been extremely careful and her symptoms were not simply due to REALLY bad sex (you never know…), they decided to test the semen. They brought the poor guy in and demanded two semen samples, one before, and one four hours after eating Brazil nuts (no word on whether his girlfriend was allowed to help him obtain the sample, my guess is he had to go it alone). They then took the samples, and performed a prick test on the girl, where they give a small prick with a needle covered in semen underneath the skin (sounds SO FUN!). This is a common way to test for particular allergies. Often they’ll do a whole slew at once over your arm or your upper back, pricking you with all sorts of things and having you wait a few hours or even a day to see if you react (Sci has had this done before, though not with semen. Would you believe I’m allergic to watermelon?). The net result of this is that you can end up with a pile of permanent marker bits and lumps all over your back. I don’t recommend getting it done in the summer.
Anyway, the poor girl got pricked with semen! And this is what they got.
On the left you can see the after effects of a normal semen prick, while on the right we have a semen prick following the guy eating four Brazil nuts (apparently they were controlling for his past consumption, when he had had 3-4). The lighting is…questionable and somewhat misleading, but it does indeed appear that she had an allergic reaction to the semen only after her boyfriend went for the nuts, though it doesn’t look like it’s as large as they say, this could be an effect of time.
One can only imagine what the girl thought when the doctors got all excited about this. The reason they got excited is that this may be the first time that an allergen has been documented to be sexually transmitted. Not just via contact with the skin or something, but in the SEMEN. The authors think there’s no other way for the allergy to have got in there, and indeed it was really localized to the vagina.
I’m mostly surprised by how FAST the Brazil nut proteins apparently got into the seminal fluid. I mean, 3-4 hours isn’t very long. While sperm itself turns over much more slowly, the idea of the proteins from the Brazil nuts getting into the seminal fluid is not unheard of. Unfortunately, the couple broke up soon afterward (given a choice, I guess he chose the Brazil nuts), and so unfortunately they couldn’t get him to donate anymore semen to the cause. If they’d had a chance, they probably would have tried to find which proteins from the nuts in particular made it into the semen, and how long they stayed there.
I have to say I’m a little surprised we haven’t heard of this before. Maybe in most long stable relationships, the partner of the person with the allergy is a little more likely to give up eating the allergen? Or maybe many potential transmissions have been missed due to condom use (no condom use in this case). Either way, it’ll be interesting to see if more of these cases turn up. And if you’re someone who has a severe food allergy, watch your partner’s semen. You never know! And it’s probably a plenty good excuse not to swallow!
Bansal AS, Chee R, Nagendran V, Warner A, & Hayman G (2007). Dangerous liaison: sexually transmitted allergic reaction to Brazil nuts. Journal of investigational allergology & clinical immunology : official organ of the International Association of Asthmology (INTERASMA) and Sociedad Latinoamericana de Alergia e Inmunologia, 17 (3), 189-91 PMID: 17583107