Difference Between Food Intolerance and Food Allergy

10/12/07 Food allergy or intolerance? It's important to know the difference.

"If you have a food allergy, eating even the smallest amount of that food may trigger a serious reaction," says James Li, M.D., Ph.D., Mayo Clinic allergy specialist, in the December issue of Mayo Clinic Women's HealthSource. "With food intolerance, you may be able to eat small amounts of problem foods without a reaction."

With an allergy, the immune system mistakenly identifies a food as harmful, triggering immunoglobulin E (IgE) antibodies to fight the substance. Signs and symptoms usually develop within minutes and may include tingling in the mouth, hives, swelling of the lips, face, tongue and throat, wheezing or breathing difficulties, dizziness, abdominal pain, diarrhea, nausea or vomiting. In severe cases, the airway can constrict.

Food intolerance, where a symptom is triggered by a food or substance, is much more common than food allergy. Only about 2 percent of adults and 6 percent of children have a food allergy. Food intolerance doesn't involve the immune system but can cause some of the same gastrointestinal symptoms as food allergy. For example, lactose intolerance, where people don't have the digestive enzymes to fully digest sugar in milk products, can cause bloating, cramping or diarrhea.

"It's wise to consult a physician if you have concerns or questions about your reaction to certain foods," says Dr. Li. Allergies can be diagnosed with skin and blood tests. Diagnosing food intolerance is a bigger challenge, requiring a thorough health history. Foods can trigger symptoms for a number of medical conditions, such as irritable bowel syndrome, acid reflux and migraine.