Allergies that affect the inside of the mouth and throat without affecting the rest of the body are known as oral allergy syndrome. According to the American Academy of Family Physicians, it is the most common food allergy and is present in up to 10 percent of patients with allergic rhinitis or asthma from grass, weed or tree pollen.
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Oral allergy syndrome is a result of cross-reactivity between the proteins in certain pollens and certain types of foods. Patients who develop this syndrome already have allergy symptoms, such as runny nose, sneezing and itchy eyes, to pollens. Proteins in the foods are similar to the antigens in the pollens that the patient is already sensitized to. When the patient puts these foods in his mouth, he develops a local reaction.
While a typical food allergy causes symptoms such as hives, nausea, vomiting, shortness of breath and dizziness, oral allergy syndrome causes only localized symptoms. Lip and tongue swelling as well as itching that can involve the mouth and throat are the most common symptoms. In some patients, these symptoms are so mild that they might not recognize that it is an allergic reaction. While it is thought that oral allergy syndrome does not progress to a systemic or life-threatening reaction, it is still recommended that the patient avoid the foods that cause the reaction.
Many types of fruits and vegetables can cause oral allergy syndrome. Patients who are allergic to birch pollen may have symptoms when eating apples, carrots, hazelnuts, peaches, pears or potatoes. Allergy to ragweed pollen can be related to oral allergy syndrome when eating bananas, melons and tomatoes. Grass allergy may be related to kiwis and tomato reactions. Mugwort pollen, which is primarily an issue in England, can be related to a reaction with apples, carrots, celery, kiwis, peanuts and different types of spices.
Symptoms with oral allergy syndrome most often occur in response to raw foods. Even patients who have reactions will often have no symptoms when the food is cooked. It is thought that this is related to the denaturing of the proteins causing the symptoms when the food is heated. Patients should avoid foods to which they have previously had symptoms and if the food is ingested accidentally should stop eating it immediately.
Any patient with symptoms of tingling and itching in the mouth or swelling of the lips should be evaluated by an allergy specialist. Even though it is thought that oral allergy syndrome is unlikely to be a life-threatening reaction, it is difficult to distinguish oral allergy syndrome from a typical food allergy. A typical food allergy can be life-threatening and patients with this diagnosis carry epinephrine with them to reverse a reaction if the food is accidentally ingested. An expert should diagnose oral allergy syndrome and perform any needed testing to ensure that a typical food allergy is not mischaracterized as oral allergy syndrome.