University Health System Blog

Dr. Mary Beth Hogan answers the question: “What is the difference between food allergy and food intolerance?”

Food allergy is based on the presence of an allergic antibody to a specific food. Because this allergic antibody is present, a classic series of symptoms happens after ingestion of this food.

This reaction includes hives, difficulty breathing, wheezing, difficulty swallowing, vomiting , diarrhea, loss of consciousness and even potentially dying.

This reaction, when it is this severe, is called anaphylaxis and usually occurs within one to two hours of eating the allergenic food.

Milder reactions can occur with either smaller amounts of allergic antibody or smaller amounts of food ingestion. Treatment for this severe reaction is total food avoidance including trace amounts and carrying an epipen in case of severe reaction.

Some people may express problems of atopic dermatitis breakouts when having the allergic antibody and ingestion the problematic food.

A food intolerance involves possibilities other than the anaphylaxis or eczema.

These include lactose intolerance due to the lack of the enzyme that processes the sugar (lactose) present in milk. Bloating, cramping, or diarrhea may happen.

Milk may also cause nasal congestion when it combines with post-nasal drip to make it thicker.

Other people may have gastroesophageal reflux symptoms of pain or the sensation of food going up and down the feeding tube (esophagus) when ingesting the problematic food.

These food intolerance problems are usually dose dependent, meaning small amounts of food may not cause a reaction, but larger amounts of food will.

Mary Beth Hogan, M.D. is professor of pediatrics and section chief  of pediatric allergy, immunology and pulmonary medicine at the University of Nevada School of Medicine and University Health System. Dr. Hogan is based out of Reno, Nevada.

Have a question? University Health System doctors answer select questions from readers like you.