Baylor College of Medicine

The difference between food allergy and food intolerance

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Dr. Carla Davis explains the important differences between a food allergy and a food intolerance.

If you have a bad reaction after eating certain foods, it can be hard to tell if you are experiencing the symptoms of a food allergy or a food intolerance. One Baylor College of Medicine expert explains the important differences between the two.

“A food allergy is when the body’s immune system is activated against a food and causes an allergic reaction with typical symptoms, such as hives. On the other hand, food intolerance is when the immune system is not involved but there’s another reason for a reaction in the body, and typical allergic symptoms do not occur,” said Dr. Carla Davis, associate professor of pediatrics in the section of immunology, allergy, and rheumatology.

Davis offered a few examples of different intolerances that people can have. One example is being lactose intolerant. If a person does not have lactase, the enzyme needed to break down lactose, then more water is brought into the gut and that can result in diarrhea or bloating. Another example of intolerance would be if a person eats fish that has not been refrigerated appropriately, causing a buildup of histidine, which is metabolized by bacteria to histamine, causing flushing and a fast heart rate. Another example might be someone who eats or drinks a caffeine containing food and has a jittery feeling and/or an increase in heart rate.

It is important to make the distinction between a food allergy and a food intolerance, Davis said. Food allergies carry potentially severe consequences, including fatal food anaphylaxis, she said. Some food allergies are not life threatening but can cause itching on the skin or worsening of an allergic condition on the skin like eczema over a period of days or weeks.

The classic symptoms of a life-threatening food allergy include hives, skin swelling, swelling of the lips, tongue or throat, a drop in blood pressure, difficulty breathing, wheezing, coughing, severe crampy abdominal pain and vomiting, Davis said.

There are two tests that are commonly used to determine if someone has food allergies, she said. The first is a skin test where a liquid with the food protein is placed on the skin and the skin is pricked so that it enters the epidermis. If a hive develops, that is an indication a food might cause an allergic reaction if the food is eaten. The second test is a blood test that examines an antibody called immunoglobulin E specific for a certain food. If the level of this food-specific allergy antibody is high, there is a higher likelihood of the person having an allergic reaction if they eat it. However, neither of these tests is 100 percent accurate, and the best way to determine if food allergies exist is an oral food challenge under a physician’s supervision.

When it comes to managing life threatening food allergy, Davis recommends complete avoidance of the food and carrying an antihistamine like Benadryl for mild reactions and injectable epinephrine for severe reactions. She also suggests people with severe allergies, especially life threatening ones, find support groups because this diagnosis can be socially isolating and anxiety provoking.

For a food intolerance, Davis said it’s important to try to figure out the cause because some of the reasons for food intolerance can be treated. For example, lactose intolerance can be treated by taking lactase tablets before eating a food containing lactose. She said it’s also important for a person with a food intolerance to keep in mind they should not be overly anxious or nervous about accidental exposures because it’s not a life threatening situation.

“A good place to start if someone thinks they have a food allergy or a food intolerance is to see a board-certified allergist. An allergist would know best how to interpret the tests as well as the clinical history and be able to make a determination,” Davis said.

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