Most of what I said about kissing applies to genitally penetrating intercourse, too. It is not uncommon for people to develop hives as a result of the vibration, pressure, heat and friction of intercourse. Swelling after sex, called postcoital edema, is also not unusual. Sex is also a known trigger for asthma and rhinitis. Several aspects of sex, including the heat and emotion, can activate the autonomic nervous system and cause release of mast cell mediators. Importantly, studies have revealed that the allergic effects of sex are not due to the physical exertion (ie. exercise anaphylaxis).
While local reactions are more common, there is precedent for sex causing multisystem allergic response or anaphylaxis. The person receiving the vaginal penetration is more likely to have anaphylaxis following sex, especially if they are strongly sensitized to food or medications. Seminal fluid can contain food or drug allergens. Aspirin and penicillin derivatives have been reported to cause allergic reactions from sex, called postcoital hypersensitivity. Transfer of pollens from the clothes or skin of the partner can also cause allergic reactions.
One product we have not yet discussed that can cause contact dermatitis and anaphylaxis is condoms. 25% of reactions to latex condoms cause hives over large portions of the body, angioedema and respiratory symptoms. There are latex alternative condoms, but many patients react to those as well.
Vaginally penetrating intercourse often causes microscopic tearing, mostly due to inadequate lubrication. As a former sex educator, if you think you are using enough lubrication, you are not. It is my personal experience that water based lubricants are better tolerated by most allergy patients for vaginal intercourse. Silicone lubricant is popular because it’s not absorbed by the body and is therefore slicker, whereas water based lubricant often requires reapplication. But that’s okay. That’s why you get a whole bottle.
Contributing to the insufficient lubrication is the fact that most people don’t engage in long enough foreplay. Foreplay provides a number of benefits: it increases naturally secreted vaginal lubrication, increases blood flow to the vagina and tells the cervix to get out of the way. 20 minutes of foreplay is often recommended as a rule of thumb in order to get the vagina in order before penetrating intercourse.
Moisture, friction and heat can cause the vulvar skin to break down. Estrogen plays a large role in keeping this tissue strong and undamaged. Urine on the skin can cause contact dermatitis. Malnutrition and history of genital infections can also contribute towards the reactivity of the tissue. It is also possible to be IgE positive for Candida albicans, a yeast that lives normally in the vagina. Inflammation can upset the balance of the normal flora, resulting not only in vaginal infections but a literal allergy to Candida.
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