Oral Allergy Syndrome (OAS)


  • Patient is allergic to birch, grass or ragweed pollens which contain a protein found in many plants therefore cross reacting with a variety of fruits and nuts
  • Not actually allergic to the fruits or nuts themselves
Cross- reactivity:

Pollen                                  Cross-Reacting Foods

Birch                                      Almonds       Kiwi
                                                Apple            Parsley
                                                Apricots        Parsnip
                                                Carrots          Peach
                                                Celery            Pear
                                                Cherry           Plum
                                                Fennel           Potato
                                                Hazelnut        Walnut

Ragweed                               Banana            Honeydew
                                                Cantaloupe      Watermelon
                                                Cucumber        Zucchini

Grass                                     Celery

Symptoms (to fresh fruits and nuts)
  • Tingling/itchy mouth, lips, throat
  • Possible throat tightening, lip swelling, itchy ears
  • Can eat the foods cooked or processed
  • Does not usually progress to anaphylaxis
  • By clinical history mainly
  • Skin testing to commercial extracts usually negative, but skin test positive on fresh food testing
  • Skin test positive to cross-reacting pollen (birch, grass, ragweed)
  • Avoid fresh fruit or nuts.  May eat the fruits cooked or processed
  • Usually does not require Epipen unless has symptoms of throat closing or other systemic symptoms or has positive skin test to the commercial extracts
*** Created by Dr. Ellie Tsai MD, FRCPC Kingston Allergy and Asthma 613-546-6673***

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