Locking lips and making other intimate contact poses a risk of serious allergic reactions for some people with highly sensitive allergies, according to research from the American College of Allergy, Asthma and Immunology (ACAAI) and reported by HealthDay News.

Allergic reactions from kissing are relatively rare, but they do happen. The reactions are caused by allergens in food or medication that stay in saliva after they’ve been ingested. Even if you brush your teeth or rinse out your mouth? Yup. (Although brushing and rinsing can help, they can’t eliminate the risk.)

“We’re talking about those few whose immune system can react vigorously to a minute amount of allergen,” explained Sami Bahna, MD, president of the ACAAI. “For these people, yes, a very little quantity of food or medicine on the lips or the mouth or the saliva can cause a problem. And for these people, we’re not just talking about a passionate kiss. Even a non-passionate kiss on the cheek or the forehead can cause a severe reaction to this kind of extremely sensitive allergic individual.”

People sensitive to allergens can experience a variety of reactions—such as swollen lips or throat, rash, hives, itching and wheezing—after kissing a partner who has ingested an identified allergen. (Ultra allergen-sensitive types can develop these reactions within hours of being exposed to their partner’s saliva.)

Bahna advises partners of allergen-sensitive people to avoid the offending food or medication for 16 to 24 hours before intimate contact.

Experts suggest people let their partners know they are allergic to certain foods or medications, especially if the problem is life-threatening.

The ACAAI estimates more than 7 million Americans suffer from food allergies.

Click here for health experts’ tips on managing food allergies at home.