Food allergy or food intolerance?

Return to Index Step 1: What is an Allergy?Step 2: The Role of the Immune System Step 3: What Substances Cause Allergies?Step 4: Allergy-Related Conditions Step 5: Should You See an Allergist?Step 6: Allergy Testing and Diagnosis Step 7: Introduction to Allergy Treatment Step 8: Avoid Allergy Triggers Step 9: Types of Allergy Medication Step 10: Over-the-Counter vs Prescription Drugs Step 11: Immunotherapy Step 12: You and Your Doctor Are a Team Key Points Glossary

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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.

Food Poisoning

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.

Histamine Toxicity

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, and (technically) could also be considered a type of food poisoning.

Lactose Intolerance

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.

Food Additives

A compound that is frequently tied to adverse reactions and often confused with food allergy is monosodium glutamate (MSG. 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. Yellow dye number 5 may rarely cause hives.

Sulfites

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. 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. Fortunately, sulfite allergy is very rare.

Gluten Intolerance

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.

Psychological Triggers

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.

Other Causes

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.

Read more about food allergies:

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.

Review Date: 6/29/2011
Reviewed By: Paula J. Busse, MD, Assistant Professor of Medicine, Division of Clinical Immunology, Mount Sinai School of Medicine, New York, NY, Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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