Can You Be Allergic To Other People? Yes, And It Sounds Like The Worst Thing Ever

“You can be allergic to pretty much anything,” one doctor told Vice back in 2015. And yes: that includes humans – or at least enough bits of them as to make life really difficult.

Semen allergies

Some people want sex but can’t get it. Others don’t want it at all. But pity the poor folks who want sex, get it, and then immediately almost die because of it.

“One night […] we were lying in bed after sex and my tongue suddenly began to swell,” one woman told BBC Future earlier this year. “My partner saw what was happening, screamed, ‘You’re asphyxiating!’ and grabbed my inhaler.”

“He was able to cram my inhaler into the corner of my mouth, and he just started firing it,” she recalled. “Luckily, I was still breathing enough to draw the medicine into my lungs.”

The culprit for the reaction? Her partner’s semen – specifically, certain proteins in the seminal fluid that carries the sperm. More properly called “seminal plasma hypersensitivity”, or SPH, semen allergies are probably the best-known of these other-humans allergies, though that isn’t saying much: as of 2024, there’s only been something like 50-odd cases reported within the past few decades.

That in itself if something of a shame, though, since it’s possible as many as one-in-eight women suffer from this disorder: “a [1997] study led by allergist Jonathan Bernstein found that among women reporting postcoital symptoms, nearly 12 percent could be classified as having probable SPH,” wrote Michael Carroll, a Reader and Associate Professor in Reproductive Science at Manchester Metropolitan University, in a June 2025 article for The Conversation. 

“I conducted a small, unpublished survey in 2013 and found a similar 12 percent rate,” he added. “The true figure may be higher still.”

So how do you know if you have a semen allergy? Well, for some people, it’s pretty obvious: the earliest case on record comes from 1967, with a woman who was hospitalized after a “violent allergic reaction” after sex with her new husband – her case report lists symptoms like raised, itchy breakouts on her skin; swelling of the eyes, lips, tongue and throat; extreme difficulty breathing; severe pelvic and uterine pain; and, eventually, loss of consciousness.

For others, it’s not so obvious. “Symptoms […] can be systemic or local,” Vice’s Dr X explained – and “local reactions manifest as vulval or vaginal pain, burning, itching, and swelling which can last a couple of days.” 

Systemic reactions, on the other hand, “often begin with the local vaginal/vulval itch and swelling with the itch spreading across the body to involve the face, lips, and tongue,” she continued. “In some cases, systemic reactions can include breathing difficulties, gastrointestinal symptoms, and full-blown anaphylaxis.”

Extra-weirdly, it’s apparently possible to be allergic via one, uh, receptive orifice, but not another. Just ask the woman who, in 2019, went into anaphylactic shock from a semen allergy after anal sex – despite never having experienced such a reaction from vaginal sex.

Dudes rock

Now, there’s something you may have noticed so far, and that’s that we’ve only covered how semen allergies affect women. That’s not an oversight: “men have semen in them all the time,” pointed out Dr X, “so it would be problematic to be allergic to it.”

But that’s not to say the spermatozoically advantaged among us get off totally scot-free. While extremely rare, it is possible to be allergic to your own semen: “This condition, known as post-orgasmic illness syndrome (POIS), causes flu-like symptoms, such as fatigue, brain fog and muscle aches, immediately after ejaculation,” Carroll wrote. “It’s believed to be an autoimmune or allergic reaction.” 

“Diagnosis is tricky,” he added, “but skin testing with a man’s own semen can yield a positive reaction.”

And while there’s almost zero published research on allergies to cervicovaginal fluid, there’s anecdotal evidence at least to support the notion. “Marek Jankowski […], an assistant professor of dermatology and venereology at Nicolaus Copernicus University in Poland, says he once treated a patient who came to him after seeing a host of other doctors,” reports the BBC. 

“The patient reported that about 30 minutes after vaginal intercourse, his genitals would become red and itchy. His face would also itch after cunnilingus.”

Despite the symptoms not being so unusual for doctors to hear from patients, skepticism seems to remain over whether this is a true allergy. But, you know… it kinda sounds like one to us.

Spit and sweat

A semen allergy may make life difficult, but at least it should be easy to avoid. Other fluids, people aren’t so shy about sharing in public – which can be a problem if you’re allergic to, say, spit or sweat.

And yet, it’s possible. For the former, the culprit is almost always not the saliva itself, but some allergen within it: “If you have food allergies, having an allergic reaction immediately after kissing someone who has eaten the food or taken oral medication that you are allergic to isn’t highly unusual,” pointed out allergist Sami Bahna, then president of the American College of Allergy, Asthma and Immunology (ACAAI), in 2010. 

“But some patients react after their partner has brushed his or her teeth or several hours after eating,” Bahna continued. “It turns out that their partners’ saliva is excreting the allergen hours after the food or medicine has been absorbed by their body.”

It’s not only kissing that can provoke this kind of response – perhaps surprisingly, this is another way allergic reactions can occur from semen. With only one known case as far as we can tell, it’s extremely rare – but for the woman who, in 2007, broke out in hives after sex with her boyfriend only after he had been eating Brazil nuts, that’s cold comfort.

But perhaps worst of all must be a sweat allergy – if only because, well, we all sweat, don’t we? And indeed, this is usually talked about in terms of being allergic to one’s own sweat: you heat up, or do some exercise, start sweating, and break out in hives. 

It’s more common than you might think – and, like semen allergies, it’s not the sweat itself that sets you off, but a particular protein within it. 

But there’s no particular reason it has to be your own sweat that causes a reaction. In 1986 – after being diagnosed with an allergy to her husband’s semen, in fact – a woman was tested against her husband and sons’ sweat, which caused her to develop a wheal-and-flare reaction. It was, the case report noted, “the first reported case of allergy to human sweat” – and, you have to assume, a pretty good excuse to never do the family laundry again.

Worst of all: allergic to any fluid at all

None of these allergies sound fun, exactly – but there’s a chance you got this far and now feel short-changed. None of the examples so far, you might argue, are actually allergies to the semen, or sweat, or spit itself – rather, it’s been a reaction to some other allergen that was carried along for the ride.

But sometimes, it really is just the stuff itself that’s the problem. It’s super-rare, but there is a condition known as aquagenic urticaria – essentially, an allergy to water of any kind. “Pruritic wheals develop immediately or within minutes at the sites of contact of the skin with water, irrespective of temperature or source,” explains one 2018 case report, and “sweat, saliva, and even tears can precipitate a reaction.”

Obviously, this can make life very difficult. Never mind swimming or spas – imagine life without showers, for example, or breaking out in a rash just because of unexpected rainfall. Saliva can make you break out in a rash; even holding your beloved firstborn baby can cause a physical nightmare if they spit up or cry on you. 

It’s an allergy to other people in probably the most acute sense. No way to exposure-therapy your way out of it; even antihistamines don’t always work, leaving sufferers to sometimes just tough it out until the itching goes away.

And the kicker? After all that, you can’t even get someone to kiss it better. Now that’s irony.