When you’re sharing an intimate  moment with someone special, there might be a lot of things on your mind.

Like how happy you are together, all the  little things they do that make you smile, and that peanut butter and jelly  sandwich that you ate a few hours ago. Well, that last one might  not make the list of things you think of right before you  have sex, but maybe it should.

If your partner has an allergy  that you consumed earlier that day, you could set off their allergic reaction. Because the signs of that meal are still flowing through your saliva  and reproductive fluids. These allergic reactions have been reported in all sorts of partnerships  after all sorts of interactions.

So it’s time for us to have the talk …  about sexually transmitted allergens. [♪ INTRO] Some people are essentially  allergic to the act of sex. Of course there are workarounds, but  it’s a rude awakening when you find out for the first time that you’re allergic to  the latex of a condom or to semen itself. Nothing kills the mood like anaphylactic shock.

And if you’ve had sex before and didn’t  break into hives or get a runny nose you might think that you’re in the clear  for allergic reactions brought on by sex. But that might be a false sense of security. While it is reported less often, some  people have allergic reactions to allergens transmitted by sex, like nut  allergies triggered by your partner’s earlier meal or pharmaceutical allergies triggered by the prescription your partner just started.

So you can still have an allergic reaction  from sex even when it’s not from sex because food and drug allergies can  be triggered via saliva or semen. Take nut allergies for example. If you’re severely allergic to nuts, you probably take serious  precautions to avoid them.

But you’re not the only one who has to be careful. If your partner has had nuts anywhere  from under a minute ago to six hours ago, they could give you the legitimate kiss of  death … although death is extremely rare. It’s more likely that you’d get itchy or  have trouble breathing in a milder response.

Both of those ends of the  spectrum have been reported after people ate either Brazil nuts or  peanuts and then engaged in sexual acts. And in some cases, these people  were very careful to avoid exposure and still provoked a nut allergy. One person bathed, brushed their teeth,  cleaned their nails, waited hours, but still made their partner  itchy and short of breath.

That’s because all it takes is 50  micrograms of the allergen in your saliva. That’s less than a single crystal of salt. Researchers think that organic fluids  like saliva can carry allergenic proteins into the gastrointestinal tract  where they resist digestion, enter the bloodstream, and  travel to reproductive organs.

Once they’re there, they can be  introduced to your partner through semen or vaginal fluid and  provoke an allergic response when their antibodies recognize the allergen. And it’s not exclusive to a penis or a vagina. Basically, these allergens don’t care  what kind of intimacy you are engaged in.

They also don’t care whether your  allergy is to a food or a drug. There have been reports of  people allergic to penicillin and similar drugs having these reactions. Like, one person knew she  was allergic to penicillin but her partner was taking a different  drug that’s related to penicillin and that difference wasn’t enough to keep her from having an allergic reaction  just five minutes after sex.

So, knowing that this could happen to  anyone with a food or drug allergy, researchers wanted to know what  might prevent the allergic response. One paper, from the Journal of  Allergy and Clinical Immunology, reported the results of an experiment in  which participants ate two tablespoons of peanut butter, attempted to clear  it out of their system, and then they donated their spit to see how many  peanut buttery proteins were still left. They tried waiting, chewing  gum, brushing their teeth, rinsing their mouths, and combinations  of all of those interventions.

Now, the researchers were very careful  to say that the results may vary depending on factors like the form  of peanut consumed and what else the toothbrush has come in contact with. But they found that each of the  interventions were better than nothing. Even though one of the interventions  was sitting there and doing nothing … I guess letting time pass is something.

In fact, the proteins were usually undetectable when participants just waited an  hour after eating peanut butter. The most effective intervention that  they tested was letting time pass and eating something else that  doesn’t have nuts in the meantime. But “usually” isn’t the kind of stat you  want to rely on in life or death situations.

Like, 87% of the study  participants were in the clear, but what if you were one of the 13% that  still had some allergens floating around? Well, some academics are urging people  to discuss allergies with your hookups. You know, while you’re having  the really sexy conversation about sexually transmitted infections,  you can just toss in some allergies.

And if you’re not sure how allergic  you are or how long you should wait to be intimate with your partner  after they ingest the cursed substance, you could do a skin prick test with your  partner’s saliva or reproductive fluid. Tests where you get a bit of semen under  your skin in an easily tested location like the arm, have been  conducted and resulted in welts only when the allergen had been  consumed before semen donation. So we’re pretty confident that allergens  can travel through those fluids.

Of course, abstinence from the  allergen is always the “gold standard.” But another option is drugs. Sure, drugs might have caused  your reaction in the first place, but that doesn’t mean that all  pharmaceuticals are off limits. Generally, more mild reactions can  be treated with antihistamines.

Finally, you might be able to avoid  some exposure by using a condom. After all, they’re useful for keeping  out all sorts of stuff, not just babies! If you keep all this in mind and go in informed, allergies will not get in the way of a good time.

Subjects like sexually transmitted  allergens can be awkward for some people. Which is why we are so lucky  to have our Patreon supporters to help fund videos like these that  advertisers sometimes shy away from. Our patrons get access to  perks like the SciShow Discord, behind-the-scenes photos, and our monthly podcast.

If you’d like to join our amazing  community and help support the channel, check out patreon.com/scishow. [♪ OUTRO]