immune disorders
Food Allergy
Diagnosis of Food Allergy
Sometimes only a doctor's evaluation Sometimes skin prick tests or an allergen-specific immunoglobulin test An elimination diet Doctors suspect a food allergy based primarily on the person’s history. Usually in adults, the allergy is obvious. But diagnosing a food allergy in children may be difficult. Some food allergies may be difficult to distinguish from many other digestive problems, such as Irritable Bowel Syndrome (IBS) . If a food allergy is suspected, one of the following tests is done: Skin testing None An Allergen-specific serum IgE tests None Skin testing None Alternatively, an Allergen-specific serum IgE tests test may be done. The immune system produces a different type of IgE in response to each allergen. For example, the IgE that is produced after pollen is inhaled differs from the IgE that is produced when nuts are eaten. For the test, doctors withdraw a sample of blood and determine whether IgE in the person's blood binds to a specific allergen used for the test, such as one for peanuts. If binding occurs, the person has an allergy to that allergen. If either test identifies a particular food, that food is eliminated from the diet. If eliminating the food relieves symptoms, the food is given to the person again to see whether symptoms develop after it is eaten. When possible, this step is done as part of an oral challenge test. The oral challenge test is done to confirm the diagnosis. In anoral challenge test,the person is given another food (such as milk or applesauce) in two batches: one with the suspected food in it and one without the suspected food in it. Then the doctor observes as the person eats the food: If no symptoms develop after the suspected food is eaten, the person is not allergic to the food. If symptoms develop after the suspected food is eaten and not after the other food is eaten, the person is probably allergic to the suspected food. Other ways to identify a food allergy include elimination diets: A diet that eliminates only the food or foods suspected of causing the allergy A diet that consists only of foods not likely to cause an allergic reaction Anelimination dietmay be the only test used to diagnose a food allergy or may be used after a skin prick test or an allergen-specific IgE test. For the first type of elimination diet, the person stops eating all foods that may be causing the symptoms for about 1 week. The second type of elimination diet, which consists only of food not likely to cause allergic reactions, can be tried instead of the first type of diet. The second type of diet involves the following: Following a diet prescribed by the doctor Eating only the foods and liquids specified in the diet and only using pure products (which excludes many commercially prepared foods) There are several possible elimination diets, which vary in the foods that are eliminated and allowed. For example, one diet may eliminate beef and lamb and allow chicken. Another may eliminate lamb and poultry and allow beef. Following an elimination diet is not easy because many food products have ingredients that are not obvious or expected. For example, many rye breads contain some wheat flour. Eating in restaurants is not advisable because the person and the doctor need to know the ingredients of every meal eaten. If symptoms are not relieved after 1 week, doctors may recommend a different elimination diet. If no symptoms occur, foods are added back one at a time. Each added food is given for more than 24 hours or until symptoms appear, and thus the allergen is identified. If the person has had very severe allergic reactions to food, the doctor may ask the person to eat a small amount of a food in the office. The doctor then observes the person’s reaction to the food. People with severe food allergies should always carry antihistamines and anepinephrinesyringe in case they have a severe reaction. 