If you go to your health care provider and say, "I think I have a food allergy," your health care provider has to consider other possibilities that may cause symptoms and could be confused with food allergy, such as food intolerance.
To find out the difference between food allergy and food intolerance, your provider will go through a list of possible causes for your symptoms. This is called a differential diagnosis. This type of diagnosis helps confirm that you do indeed have a food allergy rather than a food intolerance or other illness.
One possibility is the contamination of foods with microorganisms, such as bacteria, and their products, such as toxins. Contaminated meat sometimes mimics a food allergy when it is really a type of food poisoning.
There are substances, such as histamine present in certain foods, that cause a reaction like an allergic reaction. For example, histamine can reach high levels in cheese, some wines, and certain kinds of fish such as tuna and mackerel. In fish, histamine is believed to come from contamination by bacteria, particularly in fish that are not refrigerated properly. If you eat one of these foods with a high level of histamine, you could have a reaction that strongly resembles an allergic reaction to food. This reaction is called histamine toxicity.
Another cause of food intolerance confused with a food allergy is lactose intolerance or lactase deficiency. This common food intolerance affects at least one out of ten people. Lactase is an enzyme that is in the lining of the gut. Lactase breaks down lactose, a sugar found in milk and most milk products. There is not enough lactase in the gut to digest lactose. Lactose, instead, is used by bacteria to form gas which causes bloating, abdominal pain, and sometimes diarrhea. There are tests your health care provider can use to find out whether your body can digest lactose.
Another type of food intolerance is an adverse reaction to certain products that are added to food to enhance taste, provide color, or protect against the growth of microorganisms. Compounds that are most frequently tied to adverse reactions that can be confused with food allergy are yellow dye number 5, monosodium glutamate (MSG), and sulfites. Yellow dye number 5 can cause hives, although rarely. MSG is a flavor enhancer, and, when consumed in large amounts, can cause flushing, sensations of warmth, headache, facial pressure, chest pain, or feelings of detachment in some people. These transient reactions occur rapidly after eating large amounts of food to which MSG has been added.
Sulfites can occur naturally in foods or are added to enhance crispness or prevent mold growth. Sulfites in high concentrations sometimes pose problems for people with severe asthma. Sulfites can give off a gas called sulfur dioxide, which the person with asthma inhales while eating the sulfited food. This irritates the lungs and can send an asthmatic into severe bronchospasm, a constriction of the lungs. Such reactions led the U.S. Food and Drug Administration (FDA) to ban sulfites as spray-on preservatives in fresh fruits and vegetables. But they are still used in some foods and are made naturally during the fermentation of wine, for example.
Gluten intolerance is associated with the disease called gluten-sensitive enteropathy or celiac disease. It happens if your immune system responds abnormally to gluten, which is a part of wheat and some other grains.
Some people may have a food intolerance that has a psychological trigger. In selected cases, a careful psychiatric evaluation may identify an unpleasant event in that person's life, often during childhood, tied to eating a particular food. The eating of that food years later, even as an adult, is associated with a rush of unpleasant sensations that can resemble an allergic reaction to food.
There are several other conditions, including ulcers and cancers of the GI tract, that cause some of the same symptoms as food allergy. These problems include vomiting, diarrhea, and cramping abdominal pain made worse by eating.
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Created by the National Institute of Allergy and Infectious Diseases. Modified and updated by A.D.A.M., Inc. Image copyright A.D.A.M., Inc.
Alan Greene, M.D., F.A.A.P., Department of Pediatrics, Packard Children's Hospital, Stanford University School of Medicine; Chief Medical Officer, A.D.A.M., Inc.
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