Oral or Food Allergy Syn¬drome is characterized by pharynx itching and tingling after ingestion of raw fruits and vegetables especially in patients with seasonal allergic rhinitis (Hay Fever). Symptoms usually occur within minutes of ingestion of raw fruits and vegetables, are gen¬erally short-lived, and typically do not occur if the fruits or vegetables are cooked or canned.
In most of the patients symptoms are confined to the mouth and pharynx but in a small percentage of patients’ OAS may cause systemic reactions, which are considered to be true food-induced anaphylactic reactions. This is why food allergy testing is recommended to distinguish between true food allergy and OSA. Fruits and vegetable that cause OAS are negative in allergy testing because the protein that cause the symptoms are destroyed during preparation of the allergens for testing while it is positive in true food induced systemic reaction.
Avoidance of triggering fruits, vegetable and nuts is the best management option. Immunotherapy to the cross reactive ¬pollens may be beneficial for the treatment OAS. Few patients can experience Angioedema of the pharynx and Anaphylaxis with OAS. Therefore, strict avoidance of OAS-triggering foods is recommended. Patients with history of Angioedema or Anaphylaxis with food should carry and use Epipen in emergency because they do not have OAS but food allergies.
List of food that cross-react with Fruits & Vegetables:
Symptoms are caused by a heat- labile protein in fruits, vegetables, and nuts those cross-reacts with proteins in pollens. Birch-allergic patients will typically react to apple pears, carrots, celery, potatoes, hazelnuts, and kiwi. Ragweed-allergic patients usually, have problems with watermelon, cantaloupe, honeydew and bananas. Mugwort (weed) allergic patients may have symptoms to apples, carrots, celery, coriander, fennel, and melons. Grass-allergic patients tend to react to melons, oranges, and tomatoes.