Oral allergy syndrome (OAS) is when plant proteins from pollen and fruits or vegetables react with each other. This occurs when a child or adult with a pollen allergy eats a raw fresh fruit or vegetable. The immune system sees the plant protein as pollen which causes an allergic reaction. Peeling the skin or cooking the food will often change the protein enough to prevent this.

OAS is most common in people with asthma or hay fever from tree pollen. It seems to affect adults more than children. Not all who have these allergies will get OAS.


  • Itchy mouth or ears

  • Scratchy throat

  • Swelling of the lips, mouth, tongue and throat

Symptoms most often go away once you remove the food from your diet.

Common Causes

  • Birch pollen: apple, almond, apricots, carrot, celery, cherry, hazelnut, kiwi, nectarines, peach, pear, plum, prunes, fennel, parsley, coriander, parsnips, hazelnuts, and walnuts

  • Grass pollen: celery, melons, oranges, peaches, tomato

  • Ragweed pollen: banana, cucumber, melons, sunflower seeds, zucchini, dandelions, chamomile tea

  • Alder pollen: celery, pears, apples, almonds, cherries, hazelnuts, peaches, parsley

  • Latex: bananas, avocado, kiwi, chestnuts, papaya

  • Mugwort: celery, pears, apples, almonds, cherries, hazelnuts, peaches, parsley, coriander, sunflower, peppers

How It Is Diagnosed

Your doctor will review your health history. In some cases, you may need a skin test or oral food test. Some reactions can be severe. Ask your doctor if you need an EpiPen®.