It’s probably happened to you: You take a bite of an apple, a kiwi or some berries and suddenly feel itchy around your mouth, even though you’re pretty sure you’re not allergic to the fruit you just ate. Why does that happen?
Experts refer to the phenomenon as oral allergy syndrome (OAS), also known as pollen fruit syndrome (PFT). Indisposition is quite common and is the result of cross-reactivity. Bottom line: Your body recognizes the proteins in the fresh fruit you just ate as similar to those found in pollen, which you’re actually allergic to.
What is oral allergy syndrome?
According to the American Academy of Allergy, Asthma, and Immunology, OAS is “a form of contact allergic reaction that occurs from mouth and throat contact with raw fruits and vegetables.” The most common symptoms, which usually occur immediately after ingestion, are “itching or swelling of the mouth, face, lips, tongue, and throat.”
“It is usually a reaction to fresh fruits, nuts, or vegetables that develops in patients who have hay fever, which is an allergy to tree, grass, or wheat pollen,” explained Dr. Svetlana Kriegel , a board-certified allergist at the University of Toledo. Faculty of Medicine and Life Sciences and University of Toledo Medical Center. “About 15% of patients have a reaction to fresh fruits and vegetables because the immune system mistakes the fruit protein for the pollen protein.” Your body literally thinks you just ingested the type of pollen you’re allergic to.
“In terms of ‘real’ food allergies, there are more than 180 foods known to cause them and some of them are fruits and nuts,” explained Dr. Katie Marks-Cogan, chief allergist at Ready, Set, Food! “But when you talk about these foods specifically, the reaction is usually caused by cross-reactivity and this syndrome.”
The most common pollen allergies associated with OAS are birch trees, grass and certain types of wheat, he noted.
What are cross reactants?
Broadly speaking, there are four categories of environmental allergens that cross-react with the types of fruits, vegetables, and nuts that cause allergy-like reactions.
This chart from the American Academy of Allergy, Asthma, and Immunology is tremendously helpful in tracking down the foods that cause reactions.
Just as certain fruits are in season during specific times of the year, specific types of pollen are more prominent during certain months. That is to say: the reaction that many people associate with summer fruits is not relegated to that season, but simply indicates a sensitivity to a type of pollen. Some people deal with allergy-like symptoms during the winter, spring, and fall as well after eating foods that are not prominent in the summer months.
What are the symptoms of oral allergy syndrome?
There are some important things to keep in mind when analyzing the symptoms of OAS.
First of all, the symptoms are usually relegated to the mouth. “When we digest fruits, vegetables and nuts, the protein breaks down in our system and it no longer looks like it did when it first caused the reaction,” explained Marks-Cogan. As a result, the most common symptoms include itching, tingling, and perhaps burning of the mouth, lips, and throat. Sometimes, however, watery eyes and nose and some sneezing can occur.
If you have an anaphylactic-like reaction to consuming any of these foods, you could actually be allergic to the fruits, vegetables, or nuts themselves, and not simply displaying a sensitivity to their cross-reacting pollen.
Is there any way to prevent a reaction?
The easiest way to avoid having a reaction to any of these fruits, vegetables, and nuts, of course, is to avoid eating them altogether. Cooking them or maybe even microwaving them for a few seconds could also help you avoid symptoms.
Interestingly, the reactions do not usually occur when people consume the food in a non-raw condition, such as canned or cooked. This is because cooking fruits, vegetables and nuts actually changes their protein composition and the immune system will no longer associate that protein with the other allergens. So if you’re sensitive to raw peaches, for example, you may not experience the same symptoms when you eat baked peach cobbler.
“All of these allergens are affected by heat,” Kriegel explained. “You can’t eat fresh apples but you can eat apple jam, for example. You can’t eat apricot, but you can eat apricot jam. That’s because, once cooked, the configuration changes.”
Eaters should also keep in mind that the main allergens are found in the skin and core (along with the seeds) of fruits, vegetables or nuts, according to Kriegel. Not eating those specific parts of the fruits could also ease the discomfort.
The most discussed treatment is allergen immunotherapy, which basically consists of receiving regular allergy shots. Once you recognize the fruits or vegetables you’re having a reaction to, you can do a skin test to check for pollen sensitization. The injections will then desensitize your body to allergens in the environment and hopefully teach your immune system not to react to them.
“Once you stop reacting to pollen, your sensitivity to fruits and vegetables goes down as well,” Kriegel said. “We use the pollen extract for the injections so that the body tolerates exposure to the protein without causing the reaction. Then the body will say, ‘I already have so much pollen in my body, why do I have a reaction when I find more when I eat, say, a cucumber or an apple?’”
Simply eating more fruits, nuts, and vegetables that are causing a reaction rather than undergoing therapy has not been shown to be successful in “getting over” the syndrome.
“There has been anecdotal evidence,” Marks-Cogan admitted. “But, as adults, it’s hard to know how much extract your body needs to ‘get used to.’ With young children, the immune system is forming, so we recommend exposure to possible allergens, but when you are older it is more difficult to determine.”
What are we going to do after the reaction?
Since these aren’t “real food allergies,” as experts have pointed out, symptoms usually go away on their own within minutes. That said, taking an antihistamine (Benadryl, for example) will help soothe any kind of itching or burning relatively quickly.
In general, doctors recommend awareness. After figuring out what kinds of fruits, vegetables, and nuts are causing a reaction, consider getting a skin test to find out what pollen you’re really allergic to.