Beware nut allergists! If you pick up people in high-class bars that have real mixed nuts, be sure to use protection! Doctors have documented a case of a 20-year-old woman whose nut allergy was triggered after her partner had eaten the nuts just before they had been intimate - making the Brazil nut the world's only sexually-transmitted food.
Every day we have more evidence that the world is a dangerous and horrifying place. Dangers lurk everywhere, including . . . in the people you trust most! Helping them along are awful little things called Brazil nuts. These nuts crack open to reveal little food packets of death. How serious they were about dispensing this kind of pain was not known until recently, when a 20-year-old woman came into a hospital in the UK suffering from a triggered nut allergy.
It was assumed that her partner had triggered her allergy, since he had been consuming Brazil nuts earlier. He swore up and down, though, that he had carefully brushed his teeth, washed out his mouth, and washed his hands and face before he came into contact with her. Doctor's were mystified, though, by the fact that the allergy hadn't been triggered until after they'd had sex. The allergies should have been triggered earlier.
At last someone came up with a novel idea. Have the boyfriend eat Brazil nuts again, and test his semen both before and afterwards. A 'skin prick test on the semen' (will horrors never cease?) showed no allergens before he consumed the nuts, but significant allergens afterwards. Although nut allergies are often triggered by kissing or touching, this is generally thought to be because particles remain on the mouth, skin, or under the fingernails. Physicians doubted that the nut proteins ended up in sweat or saliva, because the allergic reaction would have started earlier, and have been triggered in other couples. It appears that Brazil nut proteins resist digestion, which is why they generally end up in the immune system, triggering immune reactions. It seems this resistance to digestion also lets them go at least one other place.
http://io9.com/5846182/woman-nearly-dies-from-allergic-reaction-to-sexually+transmitted-brazil-nuts