15 March 2019

Allergy to humans

Love itch

Andrey Ukrainsky, N+1

In an article in the British Medical Journal Case Reports, scientists told about a case of anaphylactic shock in a woman during oral sex. The media reacted to this with headlines like "A woman was found allergic to sex," although the reaction was presumably to amoxicillin in the sperm of a man who was treated with it. The case is rare, more concerning drug allergies (manufacturers may have to add a new warning to the instructions) than sex in principle. But can there really be an allergy to "sex", without an admixture of antibiotics?

Allergy to antigens of a loved one or partner is not found at every step, but it really happens and can complicate life. The most common problem of this kind is the "allergy to sex".

The authors of the publication in Mount Sinai Journal of Medicine claim that only in the USA about 40 thousand women may be allergic to seminal fluid. We are talking mainly about immediate type reactions: from 1958 to 1989, 22 percent of them were anaphylaxis, a life-threatening condition. Urticaria, Quincke's edema and local manifestations (itching, pain, burning) are also described. Perhaps if the media knew about each such case, this topic would be less sensational.

It turned out to be especially curious that 40 percent of women had such a reaction at the first contact with sperm. Since allergies can manifest only after a second encounter with an allergen (sensitization is required), scientists had to look for an explanation for this phenomenon. They found it in cross-reactions.

The main allergen of seminal fluid is prostatic specific antigen (PSA), the structure of which is 70 percent similar to the structure of prostatic kallikrein, which is found in the urine and epithelium of dogs. (Mattsson et al., Basagana et al.). Thus, an allergy to semen can be obtained by innocently contacting dogs.

You can save yourself from such an allergy with the help of abstinence or a condom. If these methods are not suitable, hyposensitization with the use of sperm proteins of a sexual partner is possible.

Another, "reverse" version of "allergy to sex" is also known. In the late 1980s, scientists described several cases when local allergic symptoms (itching, burning) and subsequent vaginitis occurred in women after sexual intercourse only with certain partners. The causes of the problem differed from those described above: in the sperm of men there were antibodies – immunoglobulins E (IgE) – against vaginal microflora or vaginal secretions. In this case, men had allergies, but women had to suffer again mainly.

Perhaps, like the antibiotic from the recent news, a woman can get food allergens with sperm. An article in the Journal of Investigative Allergology and Clinical Immunology tells how a 20-year-old girl developed urticaria after having sex with a guy who had previously eaten Brazil nuts, to which she was allergic.

For the experiment, scientists took two sperm samples from a young man: one after eating nuts, the other after abstaining from them. With both samples, they conducted allergic tests for the girl: the first was positive, the second was negative. The authors believed that they were the first to describe the sexual transmission of food aplergen. It can be found that a similar case, but with walnuts, was mentioned in 1978 (Haddad et al.), but its details could not be found on the Internet.

The other known cases of people's allergies to humans are also isolated, casuistic. "Allergy to a kiss" is much rarer, you can read about it more often in the entertainment press than in a scientific journal. At the same time, it can also often turn out to be a continuation of a food allergy, a sufficient amount of allergen can be transmitted during a kiss.

Such cases have been investigated, in particular, for peanut butter. Allergists advise to refrain from food that provokes an allergy in a partner, 16-24 hours before the expected kiss.

Human saliva itself also has an allergenic potential. Journal of Allergy & Therapy in 2014 published description of urticaria and swelling around the eyes after kissing a 25-year-old girl. The allergy was confirmed by a skin test with the partner's saliva. Scientists were unable to identify immunological details in connection with the death of the patient from another cause. One of the hypotheses of the authors of the article was sensitization to lipocalin proteins, and they also noted an increase in the allergenicity of saliva in smokers.

The first example of an allergy to sweat and, possibly, a partner's hair was described in 1986 in a 46-year-old mother of two children. 10 minutes after the start of sexual intercourse, she developed blisters and redness primarily on her hands and face. At first, the couple had to try to have sex as dressed as possible, and soon they went to different rooms.

During skin tests, scientists found that the woman had allergic reactions to both sperm and her husband's sweat (tests with the material of other donors gave a less expressive reaction). They did not rule out an allergy to her husband's hair: symptoms occurred every time she cut it, an eight-millimeter blister without redness appeared during the prick test. At the same time, she cut her sons without any problems, the samples were negative.

A person's allergy to human hair, apparently, is a real rarity, with confidence it is written about only in sources that are not trustworthy. But long-haired cat owners can carry enough allergens from their pets on their heads to provoke an allergy in a sensitized person away from cat habitats.

The cases of "intolerance of people" with mast cell activation syndrome look the most radical. Thanks to BBC News, the story of a woman whose anaphylactic symptoms appeared simply from the smell of her husband became widely known, even they had to watch the same TV show in different rooms. Similarly, she reacted to many odors and food allergens.

However, this condition does not fit the definition of a common allergy, despite the similarity of symptoms. The release of mediators in mast cell activation syndrome may occur both with the participation of IdE (as with allergies) and without it.

Given the rarity of "allergy to people", this is clearly not what you should think about in the first place when you feel bad in the presence of another person. The cause of allergic symptoms in this case is more likely to be perfumes or other "alluvial" antigens. And if doctors find an allergy to sweat, saliva or hair of a partner, you can safely contact the media and become a news hero.

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