Food allergy vs. food intolerance

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People often have an unpleasant reaction to something they ate and wonder if they have a food allergy. One out of 3 people either say that they have a food allergy or that they modify the family diet because a family member is suspected of having a food allergy. But only about 3% of children have clinically proven allergic reactions to foods. In adults, the prevalence of food allergy drops to about 1% of the total population.

This difference between the clinically proven prevalence of food allergy and the public perception of the problem is in part due to reactions called "food intolerances" rather than food allergies. A food allergy, or hypersensitivity, is an abnormal response to a food that is triggered by the immune system. The immune system is not responsible for the symptoms of a food intolerance, even though these symptoms can resemble those of a food allergy.

It is extremely important for people who have true food allergies to identify them and prevent allergic reactions to food because these reactions can cause devastating illness and, in some cases, be fatal.

What happens during a food allergy reaction?

Food allergens (the food fragments responsible for an allergic reaction) are proteins within the food that usually are not broken down by the heat of cooking or by stomach acids or enzymes that digest food. As a result, they survive to cross the gastrointestinal lining, enter the bloodstream, and go to target organs, causing allergic reactions throughout the body.

The complex process of digestion affects the timing and the location of a reaction. If people are allergic to a particular food, for example, they may first experience itching in the mouth as they start to eat the food. After the food is digested in the stomach, abdominal symptoms such as vomiting, diarrhea, or pain may start.

When the food allergens enter and travel through the bloodstream, they can cause a drop in blood pressure. As the allergens reach the skin, they can induce hives or eczema, or when they reach the lungs, they may cause asthma. All of this takes place within a few minutes to an hour.

Source: National Institute of Allergy and Infectious Diseases