What is Oral Allergy Syndrome (OAS)?

Oral Allergy Syndrome (OAS)  occurs due to a cross-reactivity between proteins found in certain foods that the immune system recognizes as similar to those found in pollens.  Eating these foods can cause an allergic reaction because the immune system mistakenly recognizes the food protein as pollen protein.  

Symptoms usually appear immediately after eating raw fruits and vegetables, and most commonly include:

  • itching of the mouth and throat 
  • also swelling of the mouth, face, lips, or tongue.  
  • Rarely, OAS will result in severe throat swelling or even  anaphylaxis

There is no specific test for OAS, but frequently patients will demonstrate positive skin tests to cross reactive pollens.  These commonly include

  • Tree pollen: peach, apple, pear, kiwi, plum, cherry, coriander, fennel, parsley, celery, carrot
  • Grass pollen: peach, celery, tomato, melon, orange
  • Ragweed pollen: banana, cucumber, melon, zucchini

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