What is Oral Allergy Syndrome? (OAS)
Updated: Dec 26, 2018
Many people don't seem to quite understand what exactly oral allergy syndrome is, more commonly now known as pollen food syndrome. Although it is a type of allergic reaction, it is much different than being allergic to a specific food and experiencing life threatening allergic reactions known as anaphylaxis.
OAS reactions are actually caused by cross-reacting allergens found in both pollen and various types of food. The most common foods that these cross-reacting allergens are found in with people who experience OAS are raw fruits and vegetables, as well as tree nuts, grains, and spices.
How does this cross-reaction cause an allergic reaction exactly? It has to do with how the immune system recognizes the pollen and similar proteins in the food as those found in the environment.
Let's talk about the most common types of allergens found in the environment. These include birch pollen, grass pollen and ragweed pollen. Although not everyone with allergies to pollens experiences reactions when eating certain foods, about 50%-75% of adults do according to the American Academy of Allergy, Asthma, & Immunology.
Let's say you are allergic to ragweed pollen, you might then react to bananas, cucumbers, melons and sunflower seeds. Or if you were allergic to birch pollen, you might react to apples, almonds, carrots, kiwis and peaches.
The interesting part about OAS is that when these foods are heated, these cross-reactive proteins actually break down, meaning that if you react to the food raw, you will probably not react to it when it's cooked. This could include baking, boiling, or even sometimes just microwaving for example an apple for a few seconds.
Sometimes, the cross-reactive proteins you experience to the fruit or vegetable are found in the peel, meaning that if you took an apple and peeled it, you wouldn't experience a reaction even when eating it raw.
The most common symptoms of an OAS reaction include itchiness or swelling of the mouth, lip, tongue or throat. It is extremely rare for an OAS reaction to lead to anaphylaxis, and if it does then it would probably be smart to do some additional allergy testing and conduct some oral food challenges at your doctor's office.
OAS reactions are usually localized to the mouth area, as when the cross-reactive proteins go through the digestive system, they are broken down and therefore your body does not react to it anymore.
This is strictly for OAS reactions and not for specific food allergies. Although OAS reactions react very well to antihistamines, if you begin experiencing trouble breathing, always inject epinephrine if you have it and go to the emergency room!