Food Allergies Part 3: OAS (Oral Allergy Syndrome)

By Ellen Marie Alonso Street, LMP Dietetic Intern

Oral food allergy syndrome affects the mouth and throat, causing irritation, itchiness and swelling within minutes of consuming “trigger” foods, or foods that cause an allergic reaction. Though severe reactions are less common, some people can experience throat swelling and anaphylactic reactions after eating a trigger food.

Most people with OAS have hay fever (allergies to ragweed, birch, grass, mugwort, alder, and/or latex), and the proteins found in pollen are a lot like those found in foods like fruits and vegetables (which makes sense since these crops require flower pollination!). The cross-reaction between pollens and fruit and vegetable cultivation is the root cause of this allergy. The body responds to food pollen proteins the same way it responds to other types of pollen proteins.

OAS is most common among older children, adolescents, and adults and can be diagnosed with lab tests for pollen allergies and food challenges. Interestingly, someone with OAS can eat a certain food for years and then suddenly develop an allergic reaction to it. Eating fresh fruits and/or vegetables usually trigger allergic reactions in people with OAS, although usually cooked fruits or vegetables aren’t a problem because heat changes the protein so much that it no longer resembles pollen protein.

Sources:

https://acaai.org/allergies/types/food-allergies/types-food-allergy/oral-allergy-syndrome
https://www.aaaai.org/conditions-and-treatments/library/allergy-library/outdoor-food-allergies-relate
https://www.chop.edu/conditions-diseases/oral-allergy-syndrome-oas