Food Allergy FAQs
Q: What is a food allergy?
A: Food allergies are caused by the production of IgE antibodies that recognize specific proteins from specific foods. When a person ingests these foods, the IgE antibodies bind to the proteins and cause the release of a chemical called histamine. Histamine is responsible for the symptoms associated with allergic reactions to foods.
Q: What foods cause allergies?
A: A person can be allergic to any food. The most common foods, however, are milk, egg, wheat, soy, peanut/nuts, and shellfish/fish. People can be allergic to multiple foods. Children often outgrow certain food allergies. Peanut and seafood allergies often persist into adulthood. It is possible to develop a new food allergy as an adult.
Q: How are food allergies diagnosed?
A: There are three types of allergy testing for foods. This includes skin prick testing, specific IgE testing, and an oral food challenge.
Allergy skin prick testing involves placing drops of a protein extract from a specific food onto the back and pricking a small amount of the extract into the outer layer of skin. If a wheel (a small, itchy bump like a mosquito bite) develops, then a patient is potentially allergic to that food. Testing takes 20 minutes and the results are read at the end of the test. The larger the wheel, the more likely a person is allergic to that particular food.
Specific IgE testing is a laboratory blood test that detects the presence of IgE antibodies that recognize specific foods. This test often produces false positives, so it is often used in conjunction with skin prick testing to determine the likelihood of a food allergy. The higher the specific IgE value, the more likely a person is allergic to that food.
Oral food challenge is the gold standard for food allergy diagnosis. As the name implies, patients ingest food suspected of causing an allergic reaction in the controlled setting of an allergist’s office. The food is usually given in increasing amounts over a period of time. The patient is monitored closely for any signs of an allergic reaction. If an allergic reaction occurs, it is immediately treated and the diagnosis of a food allergy is confirmed. If no reactions occur, the patient is definitively not allergic that that food.
Q: What about specific IgG (not IgE) food allergy testing?
A: Patients often ask about specific IgG testing to evaluate food allergies. In general, board certified allergists do not consider IgG testing useful. IgG antibodies are not responsible for allergic reactions. IgE antibodies recognize food proteins. IgE antibodies are responsible for allergic reactions through the release of histamine. IgG does not do that.
Unfortunately, patients who receive IgG testing are often found to be sensitized to multiple foods that they are then persuaded to avoid without any literature evidence that IgG is responsible for any allergic reactions. We do not perform specific IgG testing at the Food Allergy Center of Plano.
Q: How are good allergies treated?
A: Avoidance is the key to food allergy treatment. The Food Allergy Center of Plano has a registered dietitian on staff to help the patient understand which foods are safe to eat and which should be avoided. It is also important that the patient continues to meet nutritional requirements while on a restricted diet prescription. Our dietitian will conduct a complete nutrition assessment and put together a plan that will ensure proper growth (for children) and that all nutrition needs are being met. A complete 90-minute initial consultation will be done, and you will leave with an education folder filled with practical ways to implement the new diet that are specific to your or your child’s particular preferences and lifestyle. You will also receive a customized starter-shopping list that will list brands and manufacturers for foods that will replace allergenic ones that are currently in the diet. It is a systematic approach that will make transitioning to the new diet very achievable. Ongoing communication with your dietitian will be available as needed, as we understand the apprehension of making major changes in the way you or your child eats every day.
Children often outgrow certain food allergies, so allergists usually repeat allergy testing on a yearly basis. If repeat skin testing shows a significant decrease in the size of the wheel and specific IgE testing shows a decrease in the absolute value, the likelihood of an allergic reaction to that food also decreases.
Q: What is the role of a dietician in the treatment of food allergies?
A: It is important that patients continue to meet nutritional requirements while on a restricted diet prescription. Our dietitian will conduct a complete nutrition assessment and put together a plan that will ensure proper growth (for children) and that all nutrition needs are being met. A complete 90-minute initial consultation will be done, and you will leave with an education folder filled with practical ways to implement the new diet that are specific to your or your child’s particular preferences and lifestyle. You will also receive a customized starter-shopping list that will list brands and manufacturers for foods that will replace allergenic ones that are currently in the diet. It is a systematic approach that will make transitioning to the new diet very achievable. Ongoing communication with your dietitian will be available as needed, as we understand the apprehension of making major changes in the way you or your child eats every day.
Q: What about oral desensitization for foods such as peanut?
A: There has been a lot of media attention about oral desensitization to foods. Clinical research is currently being done regarding the use of oral desensitization to certain foods, such as peanut. Although this will likely become a viable option for the treatment of food allergies once the clinical research is completed and the data analyzed, oral desensitization is still considered experimental by most board certified allergists.
We at the Food Allergy Center of Plano will not perform oral desensitization outside of a clinical research setting until the clinical research is completed and standardized protocols are devised. We are unwilling to jeopardize the legitimate research being conducted in the field of oral desensitization by risking an adverse patient reaction with a non-standardized and unapproved treatment protocol. This is the general consensus of board certified allergists.
Q: What types of reactions do people with food allergies get?
A: Typical reactions to food allergies include hives, swelling, shortness of breath, wheezing, abdominal pain, and sensation of throat closure. Severe reactions that include two or more organ systems, such a hives (skin) and shortness of breath (lungs) are called anaphylactic reactions that require immediate treatment with intramuscular epinephrine, such as an EpiPen.
Q: What should a patient do if they accidently eat food to which they are allergic?
A: The first step in accidental exposure to an allergic food is to take an antihistamine. In many circumstances, this might be enough to prevent the development of a severe, anaphylactic reaction. Benadryl is probably the best choice, but any available antihistamine should be used.
Patients with food allergies are prescribed an EpiPen for use in the event of a severe, life threatening allergic reaction to food. Severe reactions included swelling, wheezing, shortness of breath, and sensation of throat closure. Patients will receive detailed instruction in the use of the EpiPen, so if the need to use it arises, the patient is prepared.
If a severe reaction occurs, emergency medical attention should be sought, but there should be no hesitation to use the EpiPen. The most common cause of death in a severe food allergy reaction is hesitancy in using the EpiPen.