Imagine experiencing itching, burning, swelling, or even struggling to breathe just moments after sex. For a small but growing number of women, this isn’t merely an awkward anecdote—it’s a medical condition known as seminal plasma hypersensitivity (SPH), an allergy to proteins found in semen.
First documented in 1967 when a woman was hospitalized following a “violent allergic reaction” to sex, SPH is classified as a type 1 hypersensitivity. This places it in the same category as hay fever, peanut allergies, and cat dander reactions. Symptoms can range from mild to severe, with some women experiencing localized reactions such as burning, itching, redness, and swelling of the vulva or vagina. Others may endure full-body symptoms like hives, wheezing, dizziness, runny nose, and even anaphylaxis, a potentially life-threatening immune response.
The Growing Recognition of SPH
Until 1997, SPH was thought to affect fewer than 100 women globally. However, research led by allergist Jonathan Bernstein revealed that nearly 12% of women reporting postcoital symptoms could be classified as having probable SPH. A 2024 study further reinforced these findings, suggesting that SPH is more common and more frequently misdiagnosed than previously believed.
Many cases go unreported or are misdiagnosed as sexually transmitted infections, yeast infections, or general “sensitivity.” A revealing clue is that symptoms often disappear when condoms are used, highlighting the role of seminal plasma in triggering the reactions.
The Role of Prostate-Specific Antigen
The primary allergen in SPH appears to be prostate-specific antigen (PSA), a protein found in all seminal plasma. This means that women can develop a reaction to any man’s semen, not just that of a regular partner. There is also evidence of cross-reactivity; for example, Can f 5, a protein found in dog dander, is structurally similar to human PSA. Women allergic to dogs may find themselves reacting to semen as well. In one unusual case, a woman with a Brazil nut allergy broke out in hives after sex, likely due to trace nut proteins in her partner’s semen.
Diagnosis typically begins with a detailed sexual and medical history, often followed by skin prick testing with the partner’s semen or blood tests for PSA-specific antibodies (IgE). Research has shown that testing with washed spermatozoa, free from seminal plasma, can confirm that the allergic trigger is not the sperm cells themselves but proteins in the seminal fluid.
Men and Semen Allergies
It’s not just women who can suffer from semen-related allergies. Some men may be allergic to their own semen, a condition known as post-orgasmic illness syndrome (POIS). This condition causes flu-like symptoms such as fatigue, brain fog, and muscle aches immediately after ejaculation. It is believed to be an autoimmune or allergic reaction, and diagnosis can be challenging. However, skin testing with a man’s own semen can yield a positive reaction.
Implications for Fertility
While SPH does not directly cause infertility, it can complicate conception. Avoiding the allergen is usually the most effective treatment for allergies, but this is not feasible for couples trying to conceive. Treatments for SPH include prophylactic antihistamines, anti-inflammatories, and desensitization using diluted seminal plasma. In more severe cases, couples may opt for in vitro fertilization (IVF) with washed sperm, bypassing the allergic trigger altogether.
It’s important to note that SPH is not a form of infertility. Many women with SPH have conceived successfully, some naturally and others with medical assistance.
Raising Awareness and Understanding
Despite its impact, SPH remains a largely hidden condition. Sex-related symptoms often go unspoken due to embarrassment, stigma, and a lack of awareness among healthcare providers. In Bernstein’s 1997 study, almost half of the women who experienced symptoms after sex had never been checked for SPH, and many had spent years being misdiagnosed and receiving incorrect treatment.
If sex routinely leaves you itchy, sore, or unwell—and symptoms improve with condom use—you might be allergic to semen. It is crucial to bring this hidden condition out of the shadows and into the consultation room.
This article is republished from The Conversation under a Creative Commons license. Read the original article by Michael Carroll, Reader / Associate Professor in Reproductive Science, Manchester Metropolitan University.
