Jun 23, 2026 12:00:00

A rare case of a woman struggling with infertility who was diagnosed with a 'sperm allergy.'

An allergy is a phenomenon in which the immune system overreacts to a specific substance ( allergen ) that enters the body, even though it is normally harmless. Common allergens include cedar pollen, dairy products, and cat or dog hair, but sometimes unexpected things can trigger allergic reactions. The science media outlet Live Science featured a case of a woman who was struggling with infertility and was found to have a rare 'semen allergy.'

Case report: Human seminal plasma allergy diagnosis for a woman with unexplained infertility - PMC
https://pmc.ncbi.nlm.nih.gov/articles/PMC11390391/

Diagnostic dilemma: Woman's infertility may have been caused by rare semen allergy | Live Science
https://www.livescience.com/health/diagnostic-dilemma-womans-infertility-may-have-been-caused-by-rare-semen-allergy

A 29-year-old woman living in Lithuania , located on the eastern coast of the Baltic Sea, wanted to become pregnant with her male partner, but was having difficulty conceiving. She had tried in vitro fertilization twice, but without success, and gynecological examinations had not identified the underlying cause of her inability to conceive.

The woman had a history of asthma and had shown allergic reactions to inhaling allergens such as mold, cat hair, and dust. Therefore, she underwent tests at a medical institution to find out if her allergies were affecting her chances of becoming pregnant.

Blood tests conducted at a medical institution revealed that the woman's blood contained an abnormally high amount of eosinophils , a type of white blood cell that causes allergic reactions. Skin tests showed that, in addition to known allergens, she was also sensitive to dust mites, weed and grass pollen, insects, and dogs.

The woman was particularly sensitive to a protein called '

Can f 5 ' found in dog dander and urine. It appears that people allergic to Can f 5 may also be allergic to a similar protein found in human semen.

During a consultation with an allergist, the woman admitted to experiencing nasal congestion and sneezing after unprotected sex with her male partner. These symptoms had been overlooked during previous consultations regarding infertility.

Doctors conducted allergy tests on women using semen samples taken from their male partners. The results confirmed that the women were allergic to seminal plasma, the fluid that carries sperm.

According to the report, semen allergy can cause inflammation of the genitals, which could be a potential cause of infertility in women. However, since embryos created through in vitro fertilization do not contain semen, it is unclear whether the IVF failure was due to semen allergy.

The most common treatment for semen allergy is condom use, but the woman refused to use condoms because she wanted to have children with her partner. Additionally, a known treatment for alleviating semen allergy symptoms involves gradually increasing the concentration of semen injecting it into the body to build tolerance to the allergen, but this treatment was not feasible in Lithuania.

Instead, doctors recommended that women take antihistamines before sex to reduce the severity of allergic reactions. Antihistamines suppress the action of histamine , a neurotransmitter involved in allergic reactions and inflammation, thereby reducing allergic symptoms.

However, taking antihistamines did not alleviate the woman's allergic reaction, and she was still unable to conceive when she returned for a follow-up appointment three years later. The woman reportedly experienced new allergic reactions after coming into contact with her partner's semen, including a burning sensation in the vulva , swollen eyelids, and watery eyes, but no further treatment was recommended.

The woman's doctor stated in the report, 'This case once again demonstrates how seemingly unrelated allergic diseases can combine to cause reproductive problems, suggesting the need for a comprehensive evaluation of the causes of infertility.'