Oral Allergy Syndrome


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This syndrome, also known as OAS, is an allergic reaction that occurs in the mouth when some people eat a selection of fresh fruits, vegetables and nuts, coupled with the inhalation of certain pollens. It is a syndrome commonly found in hay fever sufferers. What happens is a basic cross reactivity between the proteins in the fresh ingredients and the proteins in the pollen.  The immune system basically gets confused by the fruit, nut and vegetable proteins and thinks they are actually pollen proteins. Since the body may already be allergic to plant pollens, a typical allergic response will occur and a huge release of the antibody IgE takes place. With OAS, these symptoms are located within the mouth are consist of itching, burning and swelling where the offending food has come into contact.

Studies have been able to link certain pollens with certain fresh fruits and vegetables and demonstrate which combinations will lead to the most likely allergic responses:

  • Ragweed is linked with melons, courgettes, bananas and cucumbers.
  • Birch tree pollen is linked  with root vegetables, soft fleshy fruits and hazelnuts.
  • Grass seeds are linked with tomatoes, peaches and potatoes.
  • Mugwort is linked with a wide variety of spices and carrots.

Diagnosis is fairly straightforward. Skin tests are done via a double prick method. The needle is first inserted into the suspected fruit or vegetable and then used to prick your skin. If the prick results in a reaction then the test is positive.

The easiest way to treat this allergy is to simply avoid the foods that cause the reaction. In many cases, the offending proteins are altered to such a degree during cooking that they cause few if any problems. Some studies suggest that immunotherapy can also be used to help reduce or even eliminate oral allergy symptoms.


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