Oral allergy syndrome (OAS)
What is it?
Oral allergy syndrome (OAS) is a food allergy response caused by eating raw plants or vegetables.
Symptoms
OAS symptoms are most commonly associated with the oral cavities, such as the itching, tingling, or swelling of the mouth, throat, or lips. Other symptoms that do not affect the mouth or throat are less common and include watery, itchy eyes, runny nose, sneezing, and nausea or stomach upset. Some individuals may also develop itching or slight swelling of the hands if they come into direct contact with peeled fruits or vegetables that cause OAS.
Causes
Allergenic proteins found in pollen of trees, weeds and other plants are also found in many raw plants and vegetables. Ingestion of such foods can therefore trigger an allergic response in the form of OAS. Allergens that cause OAS, however, are easily destroyed by the acid present in the stomach, and symptoms usually disappear soon after the food is swallowed.
Described here are pollen types and the associated foods that cause OAS symptoms:
- Individuals allergic to tree pollen may develop OAS symptoms if they consume apples, peaches, apricots, cherries, plums, pears, almonds, hazelnuts, carrots, celery, parsley, caraway, fennel, coriander, aniseed, soybeans, or peanuts.
- Individuals allergic to ragweed pollen may develop OAS symptoms if they consume melons, zucchini, cucumber, kiwi, or bananas.
- Individuals allergic to grass pollen may develop OAS symptoms if they consume melons, tomatoes, oranges, Swiss chard, or peanuts. Peeling white potatoes or direct contact with peeled white potatoes may also cause itchy, red hands.
Diagnosis
Diagnosis of OAS is based on the presence of the symptoms listed above. Allergy specialists may also conduct skin tests and food challenges (where specialists observe patients’ reactions to consumption of particular foods) in order to accurately identify allergen.
sources: http://www.webmd.com/allergies/features/oral-allergy-syndrome-foods
http://allergies.about.com/od/foodallergies/a/oas.htm