It’s probably happened to you: You take a bite of an apple, kiwi, or berry 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 this happen?
Experts call this phenomenon oral allergy syndrome (OAS), also known as pollen fruit syndrome (PFT). Indisposition is quite common and is the result of cross-reactivity. To put it simply: your body recognizes the proteins in the fresh fruits you have just eaten as similar to those present in the pollen, to which you are in fact allergic.
What is Oral Allergy Syndrome?
According to the American Academy of Allergy, Asthma & Immunology, OAS is “a form of contact allergic reaction that occurs when the mouth and throat come in 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 with hay fever, which is an allergy to tree, grass or wheat pollens,” explained the Dr. Svetlana Kriegel, certified allergist at the University of Toledo. College of Medicine and Life Sciences and Medical Center of the University of Toledo. “About 15% of patients have a reaction to fresh fruits and vegetables because the immune system confuses the protein in the fruit with the protein in the pollen.” Your body literally thinks you just ingested the type of pollen you are allergic to.
“When it comes to ‘true’ food allergies, there are over 180 foods known to cause them, and some of them are fruits and nuts,” explained Dr. Katie Marks-Cogan, lead allergist for On your marks, get set, food! “But when talking about these foods specifically, the reaction is usually caused by cross-reactivity and this syndrome.”
The most common pollen allergies associated with ODS are birches, grass and certain types of wheat, the expert noted.
What are cross reactors?
Broadly speaking, there are four categories of environmental allergens that interact with the types of fruits, vegetables, and nuts that cause allergy-like reactions.
This chart from the American Academy of Allergy, Asthma & Immunology is extremely helpful in tracking foods that cause reactions.
Just as certain fruits are in season at specific times of the year, certain types of pollen are more important in certain months. That is to say, the reaction that many people associate with summer fruits is not relegated to this season, but simply indicates a sensitivity to a type of pollen. Some people experience allergy-like symptoms during the winter, spring, and fall as well as after ingesting unimportant foods during the summer months.
What are the symptoms of oral allergy syndrome?
There are a few important things to keep in mind when analyzing VS symptoms.
First, the symptoms are usually relegated to the mouth. “As we digest fruits, vegetables, and nuts, the protein breaks down in our system and it no longer appears to be where it caused the reaction,” Marks-Cogan explained. As a result, the most common symptoms involve itching, tingling and possibly burning of the mouth, lips and throat. Sometimes, however, runny eyes and nose and sneezing can occur.
If you have an anaphylactic-like reaction to eating any of these foods, you may actually be allergic to the fruits, vegetables, or nuts themselves, not just display a cross-reactive sensitivity to their pollen.
Is there a 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 entirely. Cooking them or maybe even microwaving them for a few seconds can also help you avoid symptoms.
Interestingly enough, the reactions don’t usually occur when people consume the food in an unraw state, such as canned or cooked. Indeed, cooking fruits, vegetables and nuts actually changes their protein composition and the immune system will no longer associate said protein with various other allergens. So if you’re sensitive to raw peaches, for example, you might not experience the same symptoms when eating baked peach pie.
“All of these allergens are affected by heat,” Kriegel explained. “You can’t eat fresh apples, but you can have apple jam, for example. You can’t have apricot, but you can have apricot jam. This is because once cooked, its configuration changes.
Eaters should also keep in mind that the main allergens are found in the skin and the very core (next to the seeds) of fruits, vegetables or nuts, according to Kriegel. Not eating those specific parts of the fruit could also ease the discomfort.
The most discussed treatment is allergen immunotherapy, which basically involves getting regular allergy shots. Once you recognize the fruits or vegetables you are having a reaction to, you can do a skin test to check your pollen sensitization. The bites will then desensitize your body to allergens in the environment, hopefully teaching your immune system not to react to them.
“Once you stop reacting to pollen, your sensitivity to fruits and vegetables also decreases,” Kriegel said. “We use the pollen extract for the injections so that the body tolerates the exposure to the protein without causing a reaction. The body will then say, ‘I already have so much pollen in my body, why have a reaction when I encounter more when eating, say, a cucumber or an apple?
It has not been proven effective to “overcome” the syndrome by simply eating more fruits, nuts and vegetables that cause a reaction instead of following therapy.
“There has been anecdotal evidence,” Marks-Cogan conceded. “But, as adults, it’s hard to know how much extract your body needs to get used to it.” With small children the immune system is formed and therefore we advise exposure to possible allergens, but when you are older it is more difficult to determine.
What should we do after the reaction?
Since these aren’t “real food allergies,” as experts have noted, symptoms usually go away on their own within minutes. That being said, taking an antihistamine (Benadryl, for example) will help soothe any kind of itching or burning relatively quickly.
Overall, doctors recommend awareness. After determining what type of fruits, vegetables, and nuts cause a reaction, consider doing a skin test to find out what pollen you are actually allergic to.