Is there a difference between a food allergy and a food intolerance?

Many people think the terms food allergy and food intolerance mean the same thing, but they do not. A food intolerance, unlike a food allergy, does not involve the immune system and is not life-threatening. For example, lactose intolerance (trouble digesting the milk sugar lactose) is a common food intolerance. Symptoms may including abdominal cramps, bloating and diarrhea which are uncomfortable but they are not life threatening.

Trying to determine if a reaction is a food allergy or a food intolerance is important regardless of the trigger because the treatment for food allergy is very different than that of food intolerance.

An allergy is an immunoglobin E (IgE) antibody-mediated immune system response to a specific trigger (in this case, a food). The main problem is that your body thinks the food is attacking it. As a result, your body reacts as if the food were bacteria or viral infection. This leads to true inflammation and activates a full immune response.

As a general rule, if a food causes a symptom that is not that of a food allergy, it is a food intolerance. This means the majority of reactions are actually food intolerance. It also means there are many different causes of food intolerance, including the following:

  • foods that can directly irritate your skin or body
  • foods that can be processed into something that irritates your skin or body
  • foods that can cause a chemical response that is undesired
  • foods that can cause a normal response that is undesired

True food allergies must be distinguished from intolerances, particularly in children and teenagers, so a child is not needlessly restricted from certain foods.

Food allergies are caused by a specific, reproducible immune response to a particular structural aspect of a “problem food.” Food allergies are most commonly caused by allergic antibodies. This means the body produces a protein that reacts with an “antigen” from the particular food to release histamine, which causes adverse reactions in the digestive or respiratory systems, or on the skin. While any food can be the source of an allergic reaction, the most common food allergies are caused by peanuts, eggs, milk, shellfish, wheat, tree nuts, soy and fin fish, explains Melinda Braskett, M.D., medical director, UCLA Food and Drug Allergy Care Center.

Many food intolerances can be thought of as irritant responses rather than an immune system problem. Food intolerances can occur when a child is unable to properly digest or break down the food. For example, people with lactose intolerance are missing the enzyme lactase and have trouble digesting milk and dairy products.

In general, children with food intolerances do not have acute health risks if the food is ingested in small amounts.

Dr. Lawrence S. Friedman, MD

Food intolerance and allergies often produce similar symptoms, but they're not the same. A food allergy is an immune system reaction to a substance that is not normally dangerous to the body. Food intolerance, on the other hand, is not an allergic response and doesn't involve the immune system, but rather some other issue, such as inadequate amounts of an enzyme to digest a particular type of food.

For some people, heartburn, gas, nausea, upper abdominal stomach upset, diarrhea, cramps, and flatulence—all common symptoms of functional disorders -- may be caused by a food that simply doesn't agree with them. The problem isn't that the food is spoiled, unripe, or contaminated by bacteria, but that the body is unable to digest a particular substance. Two common types of food that cause intolerance are dairy products and grain products containing gluten.

Much confusion surrounds food intolerances versus food allergies. Food allergies are an immunologic reaction that involves specific IgE—usually to a food protein. For instance, an individual who is allergic to cow’s milk because of a reaction to milk protein has a true food allergy. On the other hand, food intolerances are defined as non-immunologic adverse food reactions. An example is a person who may have intolerance to cow’s milk because of an inability to digest the sugar lactose. Although lactose deficiency can lead to gastrointestinal symptoms from an inability to digest lactose, the response would not be classified as a food allergy, since it is not immune based.

The contents of this website are for informational purposes only and are not intended to be a substitute for professional medical advice, diagnosis, or treatment. Nor does the contents of this website constitute the establishment of a physician patient or therapeutic relationship. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

There are many ways that a person could have an adverse reaction from food, but many are not allergies. Food allergy is defined by the immune system being involved in the adverse response.

Some people are sensitive to components of food. For example, some people are very sensitive to caffeine in coffee or chocolate and will get jittery, sweaty or have heart beat irregularities that are uncomfortable. This is not an allergy.

Some people may become ill from spoiled food, where bacterial toxins cause the symptoms. Vomiting and diarrhea from spoiled food are the common symptoms. One type of food poisoning, scombroid fish poisoning, that occurs when dark meat fish spoils, result in symptoms that looked like allergy but are really food poisoning. When these dark meat fish spoil, they may release chemicals that are similar to the chemicals released in allergic reaction. However, this is not an allergy.

Intolerance is a type of food sensitivity that may be caused by a problem with digestion. The primary example is lactose intolerance or lactase deficiency. Most of the world's population has difficulty in digesting the sugar in milk, called lactose. Symptoms tend to vary based upon the amount of lactose sugar that is ingested and typically would include upset stomach, gas, bloating and loose stools. Again, this is not an allergy. An allergy involves the immune system and the typical symptoms include rashes such as hives, itching, gut symptoms, breathing symptoms or even trouble with blood circulation resulting in confusion or loss of consciousness. Unlike an intolerance, food allergies can be deadly.

Dr. Paul M. Ehrlich, MD
Allergist & Immunologist

The difference between an allergy and an intolerance is how the body handles the offending food; that is, whether the reaction involves the immune system or not. With a true food allergy, the body's immune system recognizes an allergen as foreign and produces antibodies to halt the "invasion." The most common battlefields are the mouth (swelling of the lips), digestive tract (stomach cramps, vomiting, diarrhea), skin (hives, rashes, or eczema), and the airways (wheezing or breathing). Food intolerance is much more common than allergy. The problem is not with the body's immune system, but rather with its ability to process certain compounds—hence the diarrhea and vomiting with lactose intolerance. Patients are usually deficient in the intestinal enzyme lactase, which is needed to digest milk sugar. Estimates are that about 80 percent of African Americans have lactose intolerance, as do many people of Mediterranean or Hispanic origin.

Intolerance has also been reported over the years to certain food additives, including aspartame, a sweetener; monosodium glutamate (MSG), a flavor enhancer; sulfur-based preservatives; and tartrazine, also known as FD&C Yellow No. 5, a food color. Again, these are not allergies.

Asthma Allergies Children: A Parent's Guide

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.