February 1, 2023

Do you develop rashes, itchiness, nausea, or bloating after eating a certain food? Your adverse reaction to this particular food may be a due to food allergy or it may be due to food intolerance.

Food allergy is an immunologic or immune-mediated adverse reaction to food. Food intolerance, on the other hand, is non-immunologic and is due to medical conditions like gastroesophageal reflux disease (also called GERD), gastrointestinal infections, deficiency of digestive enzymes, anatomic defects in the stomach or intestinal tract, disorders of the nervous system, metabolic diseases like diabetes mellitus, or due to toxins.

In food allergies even a small amount of food can trigger a reaction that can be unpredictable. It can progress to a severe type called anaphylaxis. In this condition, the passage ways of air going to the lungs become severely inflamed and the person cannot breathe. It is a serious, life-threatening reaction that requires immediate medical intervention. This intervention includes injection epinephrine which may not be readily available at the time of the unexpected severe reaction. There may be no skin symptoms in a severe reaction leading to anaphylaxis.

Food allergy may involve the antibody IgE (produced by plasma cells in lymph nodes) hence is classified as IgE-mediated or it may be of the non-IgE-mediated type. An allergic reaction involves the allergy cells – mast cells and basophils – which release chemicals in the body once they are activated. In general, IgE-mediated allergic reaction has a rapid onset occurring within seconds or minutes but may occur up to two hours or more from the time the food was ingested.

An exemption to typically rapid IgE-mediated reactions is the reaction to one in carbohydrate allergens in meats. This reaction that is seen mainly in adults may start four to six hours after ingestion.

Allergic reaction is usually directed to one or two foods but it may occur to multiple foods. Some studies have shown that there are increasing number of persons who react to multiple foods.

Food allergy can involve the skin, respiratory (airways and the lungs), stomach and intestines, and the heart are affected. Itching and rashes occur in about 20 percent of cases. Food allergy does not commonly cause chronic or prolonged skin itching and rashes for more than six weeks. Gastrointestinal symptoms include nausea, vomiting, abdominal pain, and diarrhea.

When do food allergies develop? Most food allergies appear in childhood but can develop in any age. In one study, 15 percent of patients with initial allergy had the problem as an adult, with a peak at age 30 years of age.

How many persons in a population have food allergy? In earlier studies, food allergy was estimated to affect eight percent of children and five percent of adults. Subsequent studies have shown higher rates in adults.

In a study of 40,0000 adults in the United States, the prevalence was noted to be about 10.8 percent. Studies are being done on the reasons for the apparent increase in food allergy among adults.

Food intolerance can affect 15 to 20 percent of the population and is even more common among persons with irritable bowel syndrome and other functional gastrointestinal disorders. About 50 to 80 percent of affected persons report consistent problems with certain foods.

With food intolerance there is difficulty digesting or metabolizing a certain food. The amount of food ingested is directly related to the severity of symptoms – the bigger the amount of food eaten the more severe the symptoms, and the food causes similar symptoms with each exposure. Symptoms of food intolerance include bloating, excessive intestinal gas, abdominal pain, and diarrhea.

There are foods that can trigger food intolerance that mimics a food allergy. These include strawberries, blueberries, chocolate, tomato, and banana. These foods naturally compounds called “biogenic amines”. These histamine-like or histamine-releasing compounds can cause skin rashes and itching, or redness around the mouth.

If a person is suspected to have adverse food reaction, consult with a pediatrician or internist is warranted. The person is then referred to an allergologist or a gastroenterologist for additional work-up.

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