"If you have food allergies, having an allergic reaction immediately after kissing someone who has eaten the food or taken oral medication that you are allergic to isn’t highly unusual," said allergist Sami Bahna, American College of Allergy, Asthma and Immunology (ACAAI) president. "But some patients react after their partner has brushed his or her teeth or several hours after eating. It turns out that their partners’ saliva is excreting the allergen hours after the food or medicine has been absorbed by their body."

"Kissing" allergies are most commonly found in people who have food or medication allergies. Symptoms include swelling of the lips or throat, rash, hives, itching and wheezing. Food allergies affect about two to three percent of adults and five to seven percent of children in the US population, or more than seven million people, according to the ACAAI.

So what are lovebirds to do? Allergists recommend that the non-allergic partner brush his or her teeth, rinse his or her mouth and avoid the offending food for 16 to 24 hours before smooching with a person who is highly allergic to that food. But even these steps may not help in some cases.

In his presentation, Dr. Bahna discussed a 30-year-old male doctor with a peanut allergy who has had recurrent anaphylaxis, a life-threatening allergic reaction. This patient developed lip swelling and itching in his mouth when his girlfriend kissed him. She had eaten peanuts two hours earlier, brushed her teeth, rinsed her mouth and chewed gum prior to seeing him.

When things turn more intimate, allergies can be disruptive as well. Allergists have seen cases of people experiencing allergies to chemicals in spermicides, lubricants, latex or even a partner’s semen. Some people develop hives or wheezing from the natural chemicals released by their body by the emotional excitement or physical exertion during sexual interaction.

For people allergic to their partner’s semen, Dr. Bahna suggests the use of condoms or desensitization (immunotherapy) by an allergist. Preventative antihistamines may be helpful in mild cases.

"There may be more who are suffering from this than we know because people may be embarrassed to bring it up," said Dr. Bahna. "But allergists can help determine what's causing the allergy and find the right treatment. No one has to suffer."