Prather Pediatric and Allergy Center - Ask Doctor Brent

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Title: Food Allergy Versus Food Interolance

Category: Lagniappe - a little extra


The most common food that causes allergy problems are peanuts, fish, shellfish, eggs, cow milk, soy protein, wheat and corn. These are all protein compounds. The proteins in these foods can cause allergies in a genetically susceptible person. This is usually easy to recognize and diagnose. It can consist of several
possible reactions including eczema rash flare-ups, hives, gastrointestinal symptoms, and respiratory symptoms ranging from runny nose to asthma. The best way to accurately diagnose these allergies is to eliminate the food for some time, say, two to four
weeks. Then challenge with a large quantity of the suspected food in a careful setting such as a doctor's office. If the symptoms come on within minutes to hours of ingestion, it is usually easy to tell if the food brought it on. This can be repeated twice if you are not sure. About 5% of the population have these type of
classic food allergy reactions. 

Many other reactions occur from foods which are not true allergy reactions but rather what we call "food intolerances". An example is tyrosine intolerance when eating chocolate. It can cause abdominal pain, flushing, or even headaches. It's caused by a chemical intolerance to tyrosine. Another example is strawberries 
which contain a histamine, a chemical actually in the strawberry itself. This can cause headaches and other symptoms which may seem to be allergies but are actually due to intolerance to the extra histamine circulating in the blood. Probably the most common
symptom caused by food intolerance is lactose intolerance present in about 80% of people world-wide. This occurs when we drink milk or other milk products in large quantity and our body cannot break down the lactose sugar in the milk. 

Other food intolerances include food poisoning. Food poisoning can occur from food being left out and can include Staphylococcus food poisoning, Salmonella food poisoning and Botulism food poisoning.  These can cause tremendous gastrointestinal symptoms such as
diarrhea, vomiting and severe cramping. 

Other food intolerances which may mimic a food allergy include gastroesophageal reflex. This is an increase of acid from the stomach moving up the esophagus after eating certain intolerant foods. This is most common when mixing heavy fatty foods and alcohol such as a big bowl of gumbo and several beers and then, lying down shortly afterwards. 

Another intolerance is called gustatory rhinitis. It is a runny nose which occurs after eating or smelling a spicy food such as highly seasoned crawfish or hot mustard or horseradish. 

It is very important to distinguish true food allergies from food intolerances. True food allergies can be quite dangerous and can advance to the point of full-blown anaphylaxis. Anaphylaxis is a total body allergic reaction with wheezing, hives, paleness, tightness of the throat and ultimately shock and possibly death. 
Patients who have food allergies, bronchial asthma, and eczema are the most high risk group for developing anaphylaxis. The most common foods to cause anaphylaxis are nuts particularly peanuts. 

Any patient with anaphylaxis to foods should carry a bracelet in case they ever ingest their allergic food accidentally. They should also carry adrenaline to reverse the life-threatening reactions and allow them time to get to the hospital. 

For more information about this interesting topic, you can contact the Food Allergy Network at 4744 Holly Avenue, Fairfax, VA 22030.