PFAS stands for pollen food allergy syndrome.  It used to be called OAS (oral allergy syndrome) but the new name better characterizes the pathogenesis.  Using highly technical immunologic terms, it is called Class II food allergy.  Class I food allergy refers to the common/classic form of food allergy where sensitivity occurs due to ingesting the food.  In Class II food allergy, the sensitivity occurs from exposure to pollen and leads to cross reactivity with a food. 

The symptoms involve immediate itching and sometimes mild swelling of the lips, tongue, mouth and throat.  Sometimes the itching can even extend from the oral cavity to the back of the nose or ears.  Occasionally these oral symptoms are accompanied by difficulty swallowing and/or nausea.  Almost always the symptoms are both self-limiting and mild.  But the immediate nature of the onset makes people fearful of possible anaphylaxis.  That is why its important to distinguish PAS from traditional food allergy issues. 

The most common pollen-food cross reactivities are:  mugwort pollen and peach and chestnut; ragweed pollen and banana, melons, kiwi and peaches; grass pollen and tomato, peach, and apple; and birch pollen and apple, apricot, carrot, celery, cherry, chestnut, hazelnut, kiwi, peanut, pear, raspberry, soybean, strawberry, tomato and walnut. 

Of interest, cooking a food can sometimes degrade the cross-reactivity protein so that PAS doesn’t occur.  Otherwise, avoidance is the best therapy.

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