Has your mouth ever felt tingly after eating a tomato? Have you had itchy lips after eating an apple? You might have oral allergy syndrome (OAS), a type of food allergy that causes mild allergic reactions in the mouth, lips, throat and face.
What is oral allergy syndrome?
Oral allergy syndrome is a typically mild allergic reaction after eating certain foods such as fruits and vegetables. Dr. Matthew Altman, an allergist with the Allergy, Asthma and Immunology Clinic at UW Medical Center - Montlake, says it can occur when the immune system of a person with pollen allergies reacts to proteins in food that resemble pollen proteins. This is called a cross-reactivity allergic reaction.
Oral allergy syndrome can occur in anyone; however, those who suffer from allergic rhinitis or hay fever are predisposed to the condition.
“It tends to be the people with bad allergic rhinitis who tend to report symptoms of OAS,” says Altman. “Usually, symptoms are reported to be worse in the spring or the summer when pollen counts are higher.”
What are the symptoms of oral allergy syndrome?
Symptoms of an oral allergy include:
- Itchy mouth or lips
- Mild swelling of the lips, tongue, mouth, face or throat
- Itchy ears
- Hives on the mouth
“If you eat a lot of the food, you might also get heartburn or an upset stomach,” says Altman. “Think about it as moving the pollen from your mouth to your stomach, but since your stomach can’t experience sensations like itchiness, it may present as some discomfort.”
You’ll usually notice symptoms immediately after eating raw fruits or vegetables, but in some cases, they can develop more than an hour later.
“It’s important to remember that symptoms are different for everyone,” says Altman. “Some family members may react to some foods, while you may not. You shouldn’t avoid a certain food if you can tolerate it. Regular exposure to a food you are not allergic or reacting to can likely prevent you from developing an allergy to that food.”
What foods can trigger oral allergy syndrome?
The foods that can trigger oral allergy syndrome depend on the type of pollen cross-reactivity.
“There are a lot of different triggers that we have found, but the ones we see most often in the Pacific Northwest include the cross-reaction of birch and alder with stone fruit such as cherries or peaches,” says Altman. “But it can happen with other foods; Johnson grass can cross-react to citrus fruits, and other allergens can react with some veggies and nuts.”
Common allergy cross-reactions with food include:
- Birch/alder tree: almonds, apples, kiwis, peaches, parsley, plums, carrots, cherries, celery and more.
- Mugwort: bell peppers, broccoli, black pepper, cauliflower, garlic, onions and more.
- Ragweed: bananas, cantaloupes, cucumbers, watermelon, honeydew and more.
- Timothy/orchard grass: oranges, tomatoes, white potatoes and more.
Luckily, if you enjoy your favorite fruits heated or cooked, you can eat them without the fear of discomfort.
“Typically, if a food is adequately heated or cooked through, you might not have symptoms,” says Altman. “Foods like pies or jams are typically fine because they’ve been cooked down. The proteins are distorted during heating, making the allergen unrecognizable to the body.”
How is oral allergy syndrome treated?
Altman emphasizes that oral allergy syndrome is a mild allergy and discourages people from changing their entire diets to avoid certain foods.
“If symptoms are mild, you don’t necessarily need to avoid the food. You could, for example, try an antihistamine or two before eating and symptoms might be largely prevented,” says Altman. “They’re not life-threatening allergies, so you don’t have to strictly avoid these foods — just be aware of how much the symptoms bother you.”
Oral allergy syndrome has no cure, but time and repeat exposure could lessen the effects of the allergy.
“Kids sometimes grow out of it, but it’s unlikely it’s going to completely go away on its own,” says Altman. “It might be something you live with or tolerate. Some people will have a good year after a bad one, which might coincide with a year when pollen is higher or lower than normal.”
Some people have found relief through other allergy treatment methods, such as allergy shots, but it’s not guaranteed that these methods will do anything specifically for OAS symptoms.
“Pollen allergies are often treated with allergy shots, but it’s hit or miss whether this can improve OAS,” says Altman. “The pollen allergy may improve with the shots, but you may still have a reaction with some foods, so we don’t often advertise the shots as a way to help with OAS.”
How to know if you have oral allergy syndrome
The only good way to tell if your after-apple mouth tingle is from OAS and nothing more serious is to find an allergist and do some allergy testing.
“Getting properly diagnosed is important,” says Altman. “Some allergies are life-threatening, so you should not just assume or self-diagnose oral allergy syndrome. Get tested by an allergist, and they can help you decide what’s safe for you to eat, what’s not safe and help you get the proper treatment.”