Women who once thought they had contracted a sexually transmitted disease may in fact be reporting symptoms of another ailment.

It's called hypersensitivity to human semen (HHS), and it affects as much as 12 percent of women, with symptoms ranging from itching, irritation, and painful urination to atopic eczema and anaphylactic shock.

Reproductive science lecturer at Manchester Metropolitan University, Dr. Michael Carroll has found the infection may affect women between the ages of 20 and 30, or roughly 20,000 to 40,000 women annually.

Due to the properties of the semen itself, women should expect symptoms of the allergy regardless of the sexual partner.

Carroll performed a skin prick test to diagnose four women with the condition. He separated the sperm from the semen to test individually which the women reacted to. Carroll's findings shed a hopeful light on an otherwise bleak situation for many couples who have faced HHS, even without knowing it.

"In addition to the reaction and physical discomfort," Carroll was quoted as saying, "women with HHS experience emotional stress due to the impact it can have on their relationships and the concerns about family planning."

And despite the painful sensation involved with the allergy, HHS does not affect a woman's fertility. Even reaching that point, however, can prove an exhausting challenge.

Clara and Jeff, a married couple, revealed to ABC news in April their ongoing struggle to have sex and start a family.

"I had this bizarre reaction," Clara said. "I had burning and swelling and redness, which was very unusual. I thought I had contracted an STD."

The couple's sex life worsened as the frustrations mounted, and eventually the two felt more like roommates than romantic partners.

"I feel like we actually started to define ourselves - minimizing things to avoid sex," Clara said. "Funny, I started thinking I wouldn't wear sexy underwear...What seemed like medical problems had bigger effects."

The couple spent 10 months without sexual contact, as Clara reported swelling and irritation after sex, along with a rawness of her skin "as if you'd put a chemical on it that caused it to burn," she said.

To treat Clara and Jeff, dilutions of Jeff's seminal fluid were administered via a syringe at regular intervals over two hours. The couple was instructed to then have sex within 12 hours, the Daily News reports.

Clara said the swelling remained, but to a far lesser degree than what it had been in the past.

Although HHS affects primarily women, men too can develop an allergy to their semen. About one in every 100 men experiences symptoms after ejaculation, indicating an allergic reaction.

Called post-orgasmic illness syndrome, the allergy stems from low testosterone levels or lack of progesterone in the brain, researchers said. Symptoms include fever, weakness, exhaustion, headache, disordered speech, irritability, and frightening dreams.

More common causes of skin and tissue irritation from sex include sensitivity to latex in condoms or chemicals used in spermicides, lubricants, or other personal care products, said the Daily News.

Since their initial treatment, Jeff and Clara have regained the ability to have sex and enjoy it.

Jeff told ABC, "I think psychologically, we are back to a sense of normalcy."