Food Allergy Testing
Food hypersensitivity can refer to both food intolerances and food allergies, which are not the same things. Food intolerances can result from the absence of specific enzymes or chemicals needed to digest a food substance. They could be a result of an abnormality in the body’s ability to absorb nutrients, or be reactions to naturally occurring chemicals in food.
Common food intolerances include lactose intolerance and hereditary fructose intolerance (lack of particular enzymes), celiac disease (caused by an immune response to gluten protein), and sensitivity to salicylate (natural chemicals in apples, citrus fruits, strawberries, tomatoes, and wine) or amine (natural chemicals occurring in chocolate, cheese, bananas, avocado, tomato or wine).
A food intolerance may be less obvious and more difficult to diagnose than a food allergy. An elimination diet may be used to isolate problem foods and chemicals, and food with additives must be avoided during testing. If symptoms have not subsided after six weeks, food intolerance is unlikely to be involved.
Food allergy is an abnormal immune response to food. When immunoglobulin (IgE) binds to food molecules, a protein in the food is usually the problem, and it triggers the release of inflammatory chemicals such as histamine. Symptoms of food allergies typically occur within minutes or several hours after exposure. Symptoms may include itchiness, swelling of the tongue, vomiting, diarrhea, hives, trouble breathing, or low blood pressure. A severe reaction is known as anaphylaxis.
Testing for food allergy
The first step in allergy testing is a thorough medical history. The doctor will ask questions to help determine whether food allergy is causing your symptoms, and will then perform a physical exam. Several proven diagnostic methods for food allergy are:
- Skin prick test only works for IgE antibodies
- Patch testing tests for delayed food reactions, determines if a specific substance causes allergic inflammation of the skin
- Blood test only detects IgE allergens
- Oral food challenge must be performed under supervision in a hospital, due to the possibility of anaphylaxis
- Depending on your medical history and initial test results, you may have to have more than one test before receiving your diagnosis.
Treatment for food allergy
Treatment is total avoidance of the foods identified as allergens, including avoidance of eating, touching, or inhaling the problematic food. A systemic reaction, anaphylaxis, requires a dose of epinephrine (EpiPen) and transport to an emergency room for further treatment. Antihistamines can block the action of histamine, which causes blood vessels to dilate and leak plasma proteins. Histamine also causes itchiness by affecting sensory nerves. Steroids can calm down immune system cells attacked by chemicals released during an allergic reaction, but steroids should not be used to treat anaphylaxis, as steroids take longer to reduce inflammation.
If you think you have a food intolerance or a food allergy, come in for a consultation with Dr. Nangrani to discuss your experiences.