If an allergic reaction to a partner's sperm sounds bad, know that men can even become allergic to their own ejaculate. Luckily, those afflicted still have reason to hope for a decent sex life.
Dermatologist and allergist Jean Pierre Allam can still remember his first sperm allergy patient.
"She had allergic reactions again and again after intercourse," said the medical director at the University Hospital Bonn.
The patient in question experienced swelling and extreme itching in the vaginal area. These so-called "local reactions" appear in about a third of the patients who react allergically to sperm.
But the majority of afflicted women experience far worse symptoms: "systemic reactions" affecting the entire body.
"It results in redness and welts on the skin with extreme itching, then escalates to breathing difficulties, dizziness and the urge to urinate and defecate," says Allam of the typical course of a reaction. "It can lead to anaphylactic shock, where the patient can fall unconscious and even die." The allergic reaction is similar to that from an insect bite from a bee or a wasp.
A little-known illness
Although a description of the allergy was first provided by a Dutch doctor in 1958, even today, few know of sperm allergies. That's due to a lack of cases described in scientific literature - exactly 100 - and a lack of statistics.
But in industrialized countries, roughly one in every 10,000 people is affected by it, doctors say.
One reason for the lack of documentation could be that women, due to feelings of shame, do not report the condition to doctors. Another is that doctors mistakenly ascribe the reaction to an infection. Diagnosing the allergy correctly is of course critical for treatment
Male sperm contains numerous substances that can trigger an allergic reaction. In the majority of cases, it's one of the body's own proteins, the prostate-specific antigen (PSA), that does it. Stephan Weidinger and Michael Köhn , both Munich-based allergists and male-health experts, were the first to publish that finding in 2005.
Many men will have already heard of PSA, which can provide a biomarker clue to doctors who analyze concentrations of PSA in the blood in cases of potential prostate cancer.
But PSA is a totally normal protein in men's prostates. In the ejaculate, PSA ensures the fluidity and mobility of the spermatozoa. Only through PSA can the sperm reach the female's egg and successfully fertilize it.
The dog connection
Initially, doctors could not explain why some patients, after their first experience with sexual intercourse, showed varying allergic reactions.
That's because typically, a strong, itchy reaction does not occur at first contact with an allergen, but only after repeated contacts.
The likely explanation for the quick allergic reaction: The patients already had developed an allergy to human PSA through contact with dogs, says allergist Allam.
"The human PSA is cross-reactive to the PSA of a dog. Seventy percent of the people who are allergic to dogs react to canine PSA," he says, adding that they react only to male, and not female, dogs.
Dog PSA probably travels in trace amounts via urine to the dog's fur. From there, it is transmitted to humans. The allergic person can then develop an allergy - first, to the PSA of dogs, and then indirectly, to the PSA of humans.
Another form of semen allergy is more closely related to existing food allergies.
In one case, for example, a woman with an allergy to Brazil nuts showed signs of a severe allergic reaction after intercourse. The cause: Her partner had consumed Brazil nuts a few hours before having sex.
"The partner had already brushed his teeth and washed his hands, because he knew his girlfriend was allergic to them," Allam says, citing the documented case. Still, the allergen was transmitted through his sperm, and the woman developed a strong case of erythema (redness, rash) and welts on the skin in the vaginal area.
Allergic to proteins
Men can have sperm allergies, too. That said, Post Orgasmic Illness Syndrome (POIS), as it's known, has not been well researched.
"The symptoms reported by patients are not absolutely typical for allergies," Allam says. "They include headaches, fatigue and flu-like symptoms that last two to seven days after ejaculation."
Nevertheless, physicians think that they could also be dealing with an allergic reaction in POIS. Through "prick tests," or skin allergy tests, which are used to test suspected allergies, it has been shown that many men affected by POIS are allergic to the proteins in their own sperm.
Condoms or antihistamines
One consequence of these particular forms of autoimmune reaction is that many patients suffering from it attempt to avoid orgasms or withdraw themselves sexually.
One option is to use condoms during intercourse, which can largely rule out the possibility of an allergic reaction (though nothing is perfectly safe).
Those who do hope to have a child, however, have three possibilities. If the symptoms appear locally and don't affect the entire body, they can use antihistamines. The drugs reduce the impact of an allergic reaction.
The next option is to desensitize themselves to sperm through hyposensibilization.
"Allergens will initially be introduced in small quantities in the vagina, and then relatively quickly in higher quantities, so that the immune system gets used to the substance," Allam says. The only disadvantage: Hyposensibilization only works when the allergen is continually applied, again and again. "In order to main tolerance, the couple has to have intercourse every three days. If that timeframe's exceeded, the tolerance can collapse and lead to a recurrence of the symptoms," the allergist says.
At the moment, researchers are trying to determine whether hyposensibilization can be achieved through medication - through something like medicine that contains PSA. There is currently no hyposensibilization medication for sperm allergies that would work long-term (as it does for hayfever). Nor is such a medication foreseeable soon.
The final option to get pregnant is artificial insemination. The sperm are freed from the PSA in various steps, are isolated and are then inserted into the ovum.
In Germany, that procedure would likely be covered by health insurance, provided an allergic reaction has already been documented.