We have excellent skin testing materials for food allergy. They have proven to be a more sensitive type of test than blood allergy tests (RAST’s). With skin prick tests, we are looking for the allergic protein, IgE, that is specific to a certain food. IgE is responsible for the most serious type of food allergy that lead to hive or welts (urticaria), swelling (angioedema), and anaphylaxis – the most severe form of food allergy reactions. If a food allergy exists, we teach the patient and their caregivers how to avoid these foods and how to prepare for accidental ingestion. Some medical professionals and non-physicians recommend certain brands of tests looking for specific-IgG to foods. We, like the American Academy of Allergy, Asthma & Immunology, believe these test lack scientific support.
If there is a questionable food allergy, we may perform a food challenge. Here we have the patient carefully eat small amounts of the given food under close medical supervision to determine if they are truly allergic. In this way, we are often able to free the patient from the fear, stigma and hassle of being labeled as allergic to a food. The patients are then able to expand their diet and enjoy life a bit more. See our detailed article about food allergies.
If you have a food allergy, your immune system overreacts to a food. This is caused by an antibody called IgE (Immunoglobulin E), which is found in people with allergies. Food allergy is more likely to develop in someone who has family members with allergies. Symptoms may occur after you consume even a tiny amount of the food.
Most allergens can cause reactions even after they are cooked or have undergone digestion in the intestines. There are some exceptions. For example, some allergens (usually fruits and vegetables) cause allergic reactions only if eaten in their raw form. Symptoms are usually limited to the mouth and throat.
The most common food allergens are the proteins in cow’s milk, eggs, peanuts, wheat, soy, fish, shellfish and tree nuts.
In some food groups, especially tree nuts and seafood, an allergy to one member of a food family may result in the person being allergic to other members of the same group. This is known as cross-reactivity.
Cross-reactivity is not as common with foods from animal groups. For example, people allergic to cow’s milk can usually eat beef, and patients allergic to eggs can usually eat chicken.
With shellfish, crustaceans (shrimp, crab and lobster) are most likely to cause an allergic reaction. Molluscan shellfish (clams, oysters, scallops, mussels, abalone, etc.) can cause allergic reactions, but reactions to these shellfish are less common. Occasionally, people are allergic to both types of shellfish.
Symptoms of allergic reactions are generally seen on the skin (hives, itchiness, swelling of the skin). Gastrointestinal symptoms may include vomiting and diarrhea. Respiratory symptoms may accompany skin and gastrointestinal symptoms, but don’t usually occur alone.
Anaphylaxis (pronounced an-a-fi-LAK-sis) is a serious allergic reaction that happens very quickly. Without immediate treatment-an injection of epinephrine (adrenalin) and expert care-anaphylaxis can be fatal. Follow-up care by an allergist/immunologist, often referred to as an allergist, is essential.
Symptoms of anaphylaxis may include difficulty breathing, dizziness or loss of consciousness. If you have any of these symptoms, particularly after eating, seek medical care immediately (call 911). Don’t wait to see if your symptoms go away or get better on their own.
An allergist is the best qualified professional to diagnose food allergy. Your allergist will take a thorough medical history, followed by a physical examination. You may be asked about contents of the foods, the frequency, seasonality, severity and nature of your symptoms and the amount of time between eating a food and any reaction.
Allergy skin tests may determine which foods, if any, trigger your allergic symptoms. In skin testing, a small amount of extract made from the food is placed on the back or arm. If a raised bump or small hive develops within 20 minutes, it indicates a possible allergy. If it does not develop, the test is negative. It is uncommon for someone with a negative skin test to have an IgE-mediated food allergy.
In certain cases, such as in patients with severe eczema, an allergy skin test cannot be done. In this case, your doctor may recommend a blood test for food-specific IgE. False positive results may occur with both skin and blood testing. Food challenges are often required to confirm the diagnosis. Food challenges are done by consuming the food in a medical setting to determine if that food causes a reaction.
Most children outgrow cow’s milk, egg, soy and wheat allergy, even if they have a history of a severe reaction. About 20% of children with peanut allergy will outgrow it. About 9% of children with tree nut allergy will outgrow it. Your allergist can help you learn when your child might outgrow a food allergy.
The best way to treat food allergy is to avoid the foods that trigger your allergy. Although it has been shown that just smelling peanut butter will not cause a reaction, sometimes food allergens can be airborne, especially in steam, and can cause reactions. Boiling or simmering seafood is a particular offender.
Always ask about ingredients when eating at restaurants or when you are eating foods prepared by family or friends.
Carefully read food labels. The United States and many other countries require that food allergens are listed in common language, for example, “milk” rather than a scientific or technical term, like “casein.”
Carry and know how to use an injectable epinephrine device to treat emergency reactions. Teach family members and other people close to you how to use epinephrine, and wear an ID bracelet that describes your allergy. If a reaction occurs, have someone take you to the emergency room, even if symptoms subside. Afterwards, get follow-up care from an allergist.
Food allergies can be confusing and isolating. For support, contact the Food Allergy & Anaphylaxis Network (FAAN) at (800) 929-4040 or visit www.foodallergy.org.
Feel Better. Live Better.
An allergist/immunologist, often referred to as an allergist, is a pediatrician or internist with at least two additional years of specialized training in the diagnosis and treatment of problems such as allergies, asthma, autoimmune diseases and the evaluation and treatment of patients with recurrent infections, such as immunodeficiency diseases.
From the American Academy of Allergy, Asthma, & Immunotherapy 2009
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