A food allergy is an immune system response by which the body creates antibodies as a reaction to certain food. Symptoms similar to those of irritable bowel syndrome (IBS) include diarrhea and abdominal pain. Other symptoms can include vomiting, hives, itching, swelling of the lips, tightness in the throat, and wheezing. Allergic symptoms usually occur within a few minutes to an hour after ingesting the causative food. Eight foods cause 90% of all allergic reactions: milk, egg, wheat, peanuts, soy, tree nuts (almonds, walnuts, pecans, etc.), fish, and shellfish.
Although relatively rare, food allergies to certain foods can also mimic or worsen symptoms of functional GI disorders. Allergies can also lead to more generalized symptoms involving skin rashes, asthma, and swelling.
Food intolerance occurs when the body cannot adequately digest a portion of a particular food, usually because of a chemical deficiency. Examples of food intolerance can include:
Lactose intolerance - People with this common disorder have difficulty digesting milk because of a deficiency of the enzyme lactase.
Congenital sucrase-isomaltase deficiency (CSID) - People this rare disorder cannot break down the sugars sucrose (a sugar found in fruits, and also known as table sugar) and maltose (the sugar found in grains).
In response to a mailed consumer questionnaire that surveyed 5,000 representative Americans, 16% reported conditions that they felt were food allergies. However, studies show that true food allergies are present in only 1-2% of adults. In people with IBS, reactions to food are rarely allergic reactions.
If a food allergy is suspected, the offending food should be eliminated from the diet and then reintroduced. If the symptoms improve on the elimination diet, and then consistently recur when the food is introduced back into the diet, formal allergy testing should be performed. Sometimes an elimination diet to exclude all known allergens can help distinguish food allergy from other symptoms.
Studies have shown that the onset of symptoms in a person can be influenced by even a mistaken belief that they have food allergies. Therefore, allergy testing is done to make a definitive diagnosis.
If you suspect you are intolerant to certain foods or that you have a food allergy, talk to your physician or consult a registered dietitian before making any drastic changes in your diet. You want to make sure you are maintaining proper nutritional balance in your diet and not disrupting your quality of life by needlessly eliminating certain beneficial foods.
Boan JF (Formerly Knowles). Dietary Factors in Gastrointestinal Diseases. IFFGD Fact Sheet No. 148; 1998.
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The Publications Library topics on food intolerance/malabsorption.