Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
A food allergy is an immune-mediated adverse reaction to a particular food. For someone with a food allergy, eating or swallowing even a tiny amount of a particular food can cause symptoms such as skin rash, nausea, vomiting, cramping, and diarrhea. Because the body is reacting to something that is otherwise harmless, this type of allergic reaction is often called a hypersensitivity reaction. Rarely, a severe allergic reaction can cause a life-threatening set of symptoms called anaphylaxis, or anaphylactic shock.
Although about 25% to 30% of people believe they have a food allergy, only about 2.5% of adults and about 6% to 8% of children, mainly younger than 6 years, have true food allergies. The rest have what is known as food intolerance -- an undesirable reaction to a food that does not involve the immune system.
It is easy to confuse food intolerance with food allergy because they can have similar symptoms. With food intolerance, however, a person usually gets only mild symptoms such as an upset stomach.
A common example of food intolerance is lactose intolerance -- a condition in which a person is missing a certain enzyme necessary to digest dairy proteins. The result is loose stools, gas, and nausea after consuming dairy products such as milk or cheese.
Another example of food intolerance is reaction to MSG. MSG, or monosodium glutamate, is a white-colored additive used to enhance the flavor of food. It is a fermented mixture of glutamic acid, sodium, and water and is used mainly in Asian cooking. Over the last decades, side effects from MSG have been related to its use in Chinese food and referred to as the Chinese restaurant syndrome. In this syndrome, MSG was suggested as the cause of the symptoms following a Chinese meal. In 1995, a new term was coined, the MSG symptom complex, to include all the reactions that were reported to be related to MSG. These reactions are not a true food allergy, and the exact cause of the reactions is unknown.
Difficulty in digesting a food. Common offenders include milk products, wheat and other grains that contain gluten, and foods that tend to cause intestinal gas, such as cabbage and beans. Food intolerance is often mistaken for food allergy, but it does not involve a histamine response against the food. Treatments include avoiding the offending food and taking supplemental products that allow that food to be adequately digested.