Don’t Limit Diet Because of Unfounded Food-Allergy Fears
MARCH 11, 2006
DENVER — Many people unnecessarily avoid certain foods because of mistaken fears about food allergies. Parents are especially prone to limiting the diets of their children. In one study, 28 percent of parents thought their children had at least one food allergy during the first three years of life. However, careful testing showed that only 8 percent of the children actually had a food allergy.
"Food allergies can be a serious, even life-threatening condition, and patients need to avoid foods that cause allergic reactions,” said National Jewish pediatric allergist David Fleischer, MD "On the other hand, unnecessarily limiting a child’s diet can create anxiety about food and make it difficult to get adequate nutrition. A careful medical history and diagnosis by a physician can clarify exactly what foods, if any, need to be avoided.”
Self-diagnosis of food allergy can be difficult. For one, a person usually consumes several foods at one sitting, making it difficult to identify the food that caused a reaction. Also, there can be a delay between eating a food and developing a reaction, adding to the difficulty of identifying exactly what caused the reaction. Furthermore, processed foods can contain substances that most people don’t even realize they are eating unless they carefully scrutinize the ingredients list.
People also often mistake food intolerance for food allergy. Food allergy occurs when the immune system mistakenly recognizes a food as harmful, and reacts against it. Allergic reactions can occur in the skin, respiratory system or gastrointestinal tract, causing swelling, hives, sneezing, nausea, abdominal pain, wheezing, shortness of breath or a drop in blood pressure. People can and do die from severe allergic reactions to food. Food intolerance occurs when the body has difficulty digesting food. It does not involve the immune system, generally causes milder reactions only in the gastrointestinal tract, and requires larger amounts of food to provoke a reaction. While both food intolerance and food allergy cause discomfort, food intolerance is not considered dangerous, and can sometimes be prevented with dietary supplements.
Dr. Fleischer suggests that people who suspect that they or their children have a food allergy keep a detailed food diary for 2-3 days before visiting a physician. Food diaries should include what you ate, when you ate it, how long after you ate it that you had a reaction, what symptoms developed, and what treatment, if any, was necessary.
“A food diary is an easy way for patients to keep track of food reactions so the exact history can be accurately conveyed to the physician,” said Dr. Fleischer.
The fastest way physicians test for allergies is the prick skin test; a drop of extract from the suspect food is placed on the skin, and a tiny needle is used to prick the skin where the drops are placed. A patient who develops a reaction at the injection site may have an allergy. However, this test doesn’t always detect allergies and may even be falsely positive. So, the physician may also do a blood test. The most common blood test, a radioallergosorbent test (RAST), measures the IgE antibodies to a specific food in your blood.
"The only definitive test for food allergy is whether a person can consume that food without an adverse reaction,” said Dr. Fleischer. An oral food challenge accomplishes this by exposing a person to the food, first by smell, then by touch, and, finally, by eating increasing amounts of it. A challenge is terminated if an adverse reaction occurs at any stage. All challenges are performed under close medical supervision, usually only at specialized allergy centers like National Jewish. Patients should not perform their own food challenges on food they believe have caused a significant reaction in the past.
Outgrowing an allergy
People do outgrow allergies, so an allergy evaluation can be helpful even if a person has been diagnosed with a food allergy. Milk, egg, soy, and wheat are common childhood allergies that children often outgrow. Peanut, tree nut, and fish allergies are more likely to extend into adulthood, but recent research has shown that some people with peanut and tree nut allergies eventually outgrow them.