What do Peanuts, Gluten, Egg, Latex and Semen all have in common?

We know it’s crunch time for your ABIM exam prep. However, we all need a moment to stretch and refresh our minds before returning to the books/Knowmedge questions. The post below by our allergy/immunology fellow Dr. Charles Feng is perfect for an ABIM study break.

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One of the reasons medicine is so intellectually stimulating is because of the wide array of rare diseases – zebras – we are able to read about, but may never see over the course of our careers. As an allergy/immunology fellow, I am fascinated by the zebras that exist in the domain of allergic diseases.

A more interesting one I recently came across is an allergy to semen.

Please, hold the snickers and refrain from crude jokes. I’m trying to be professional here.

Semen allergy, or more specifically an allergic reaction to proteins in human seminal plasma (HSP), exists in women. Given the obviously sensitive nature of this topic, there have been only 90 published case reports worldwide.

Allergic reactions to seminal plasma are Type I IgE mediated reactions. Within one hour of exposure to ejaculate, women may have localized vulvar and vaginal pruritis, followed by rhinorrhea and watery eyes. More serious symptoms include angioedema of the throat, dyspnea, wheezing, and stridor. The symptoms usually resolve within a day, although constitutional symptoms such as malaise may last for weeks.

According to the medical literature, half of the HSP reactions occur in women after their first sexual encounter. Most HSP-sensitive patients have these reactions with all sexual partners, although the occasional soul only has these reactions to a specific partner. The usual age of onset is in a woman’s 20s, and is associated with life events like pregnancy, as well as surgeries like hysterectomies.

As with many rare diseases, the clinical diagnosis is made with a thorough and probing history. First, you have to get over any embarrassment you may have about asking detailed questions about your patient’s sex life. Then, you want to inquire about allergic symptoms before and after ejaculation. Just as important, you should inquire about partners’ condom use, and whether these symptoms are prevented by condoms.

Because of the ambiguous nature of the symptoms, the differential is necessarily broad, and includes vulvodynia, vulvovaginal candidiasis, dyspareunia, and local irritant contact reactions (such as from vaginal contraceptives). Other diseases on the differential include post-coital asthma, latex allergy from condoms, and food/drug sensitivities (if a partner eats walnuts prior to intercourse, some of the nut residue can find its way to the sperm and cause problems for a nut allergic patient). With a good gynecologic exam, as well as further questioning on latex, food, and medication allergies, the differential can be narrowed.

Definitive diagnosis can be made with skin testing with seminal plasma, in which the male partner’s semen sample is centrifuged, and the upper layer with the HSP is siphoned off and applied to the woman’s skin to determine if there is a local allergic reaction. When the history is suggestive of HSP allergy but the skin test is negative, then the HSP can be concentrated by a labor-intensive procedure called column fractionation. Currently, only the allergy department at the University of Cincinnati performs this procedure—indeed, that is where a patient should be referred to if HSP allergy is suspected.

Multiple treatment options exist. First, condom use prevents sperm transfer, although there is always the risk of breakage. Second, anti-histamines taken prior to intercourse may also help, and every patient should have an EpiPen in the case of an anaphylactic reaction. Fortunately, there have been no deaths reported with HSP allergy.

Alternatively, a woman can be desensitized with immunotherapy, either intravaginally or subcutaneously. Many patients elect to undergo desensitization if they want to get pregnant. If a woman elects desensitization, then sexual intercourse is required two to three times a week in order to maintain sensitization.

As Dr. David Bernstein, who has published multiple papers on the subject, writes, “In the author’s experience, couples are generally successful with this approach.”

Given the nature of the topic, even a world-leading expert on HSP allergies cannot refrain from making a dry joke in an otherwise staid academic review article.

You can find other posts by Dr.Feng on the Knowmedge Blog. You can also find additional topics and questions directly from the Knowmedge Internal Medicine ABIM Board Exam Review Questions QVault.

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Charles Feng is an allergy / immunology fellow at UC Davis. He has worked as an internal medicine physician at Kaiser Permanente.