It probably happened to you: you bite into an apple, a kiwi or some berries and suddenly feel itchy around your mouth, even though you are pretty sure you are not allergic to the fruit you just ate. Why does this happen?
Experts call the phenomenon oral allergy syndrome (OAS), also known as pollen fruit syndrome (PFT). Indisposition is quite common and is the result of cross-reactivity. Put simply: your body recognizes the proteins in fresh fruit you just consumed as similar to those found in pollen, to which you are actually 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 upon contact of the mouth and throat with raw fruits and vegetables.” The most common symptoms, which usually occur soon after ingestion, are “itching or swelling of the mouth, face, lips, tongue and throat”.
“It is usually a reaction to fresh fruit, nuts or vegetables that develops in patients who have hay fever, which is an allergy to tree, grass or grain pollen,” explained Dr Svetlana Kriegel, a allergist certified by the University of Toledo College of Medicine and Life Sciences and University of Toledo Medical Center. “About 15 percent of patients have a reaction to fresh fruit and vegetables because the immune system mistakes the fruit proteins for pollen proteins.” Your body literally thinks you’ve just ingested the type of pollen you’re allergic to.
“In terms of ‘real’ food allergies, there are over 180 foods that have been known to cause them and some are fruits and nuts,” explained Dr Katie Marks-Cogan, chief allergist for Ready, ready, food! “But when it comes to these foods in particular, the reaction is usually caused by cross-reactivity and this syndrome.”
The most common pollen allergies associated with OAS are birch trees, grass and some types of wheat, the expert noted.
What are cross-reactors?
Generally, there are four categories of environmental allergens that cross-react with the types of fruits, vegetables and nuts that cause allergic-type reactions.
This chart from the American Academy of Allergy, Asthma & Immunology is extremely useful for tracking foods that cause reactions.
Just as some fruits are in season at specific times of the year, specific types of pollen are more important during certain months. Namely: 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 face allergy symptoms during the winter, spring, and fall even after ingesting foods that aren’t important in the summer months.
What are the symptoms of oral allergy syndrome?
There are some important things to keep in mind when analyzing OAS symptoms.
First of all, the symptoms are usually relegated to the mouth. “When we digest fruits, vegetables and nuts, the proteins are broken down in our system and it no longer looks like it did when it first caused the reaction,” Marks-Cogan explained. As a result, the most common symptoms involve itching, tingling and possibly burning in the mouth, lips and throat. Sometimes, however, runny eyes and nose and some sneezing may occur.
If you have an anaphylactic-like reaction to consuming any of these foods, you may actually be allergic to the fruit, vegetables, or nuts themselves, not simply showing 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 at all. Cooking them or maybe even microwaving them for a few seconds could help you avoid symptoms.
Interestingly, reactions do not usually occur when people consume foods in a non-raw condition, such as canned or cooked. This is because cooking fruits, vegetables and nuts actually change their protein composition and the immune system will no longer associate said protein with various other allergens. So if you are sensitive to raw peaches, for example, you may not experience the same symptoms when eating baked peach pie.
“All of these allergens are affected by heat,” explained Kriegel. “You can’t eat fresh apples, but you can eat 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 major allergens are found in the skin and heart itself (next to the seeds) of fruit, 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 consists of undergoing regular allergy injections. Once you recognize the fruit or vegetable you are reacting to, you can perform a skin test to check your sensitization to pollen. The shots 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 pollen extract for shots to make the body tolerate exposure to the protein without causing the reaction. The body will then say, ‘I already have so much pollen in my body, why have a reaction when I encounter more when I eat, say, a cucumber or an apple?’ “
It has not been shown to be able to “get over” the syndrome simply by eating more fruits, nuts and vegetables that are causing a reaction instead of going through therapy.
“There was anecdotal evidence,” admitted Marks-Cogan. “But, as an adult, it’s hard to know how much of the extract your body needs to ‘get used to’. With small children the immune system is forming and therefore we recommend exposure to possible allergens, but when you are older it is more difficult to determine “.
What should we do after the reaction?
Since these are not “true food allergies,” as noted by experts, symptoms typically subside on their own within minutes. That said, taking an antihistamine (Benadryl, for example) will help soothe any itching or burning pain relatively quickly.
Overall, doctors recommend awareness. After figuring out what kind of fruits, vegetables, and nuts are causing a reaction, he considers taking a skin test to find out which pollen you are actually allergic to.