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What are the most common foods people are allergic to?

Food allergies can turn the routine experience of eating into an adventure. While a number of different foods are known to trigger reactions, only eight account for 90 percent of all foodallergic reactions: milk, egg, peanut, tree nut, fish, shellfish, soy and wheat.

All told, about 12 million people are affected by food allergies in the United States, says Dr. Marc Riedl, assistant professor of medicine at the UCLA Medical Center. While no preventive methods for food allergies exist yet, there are some promising possibilities in the pipeline. “There is a great deal of interest in therapeutics because our current treatment is so limited,” says Riedl.

Smart Business spoke with Riedl about food allergies, how you should proceed if you suspect you have an affliction and what type of research is being conducted in this field.

From a medical standpoint, why do food allergies occur?

Allergic conditions result from a combination of genetic and environmental factors. We think of food allergies as a breakdown of something called oral tolerance — an immune mechanism by which our gastrointestinal tract learns to discriminate between harmless things, such as foods, and harmful things, such as bacteria or parasites. When someone has a food allergy, that mechanism is failing and we don’t know exactly why that is. A number of hypotheses have been put forward. Probably the most advanced one is that the microflora of the gut in young children may have changed with our recent hygienic lifestyle.

What are the common symptoms that accompany a food allergy reaction?

The primary gastrointestinal symptoms can be itching of the mouth, diarrhea, nausea or abdominal pain. Often, food allergy reactions are accompanied by skin symptoms such as hives, swelling of the lips or throat, or itching of the skin. Once in a while, respiratory symptoms like shortness of breath or nasal congestion can be observed. With the most severe reactions you get anaphylactic shock, which is accompanied by a drop of blood pressure and lightheadedness.

What is the best treatment?

The best treatment is to prevent the reactions through strict food avoidance measures. That requires a great deal of education and vigilance by the patients. In the event that an ingestion of a food allergen occurs, then treatment is focused on the use of epinephrine or injectable adrenaline.

How should people proceed if they suspect they have a food allergy?

The most important thing is to see an allergist or health care provider who has experience in dealing with food allergies. The history is very important, so patients need to pay attention to the timing and the symptoms that occur after they eat a food that they’re suspicious of. A food diary can be helpful if a patient is uncertain whether reactions are related to eating a certain food.

What kinds of tests are conducted when determining if a food allergy is present?

There are two major types of food allergy testing. The first is allergy skin testing, which consists of pricking the skin with a small amount of food allergen. If an allergic antibody is present in the immune system, then you’ll get a wheel-and-flare reaction. This is probably the best screening test that we have for food allergies because it’s very quick, efficient and easy for most patients to tolerate.

The other type of food allergy testing is blood testing, which we often call RAST IgE testing. This method involves collecting blood from a patient and sending it to the laboratory where the blood is screened for allergic antibody to specific food allergens.

There are no medications that cure food allergies. What type of research is being conducted in this area?

The first is what I’ll call more traditional medical treatment, which is taking a medication to prevent food reactions from occurring. The two that are in development right now are Anti-IgE and FAHF2.

Anti-IgE is a medication that has been used to treat severe asthma. There have been some early human trials looking at the effectiveness of this drug in preventing food allergy reactions. Unfortunately, there have been some adverse reactions in those clinical trials. As you can imagine, it’s difficult to give food-allergic people the food they’re allergic to without the risk of reactions. FAHF2 is a Chinese herbal formula that has shown some promise in preventing allergic reactions to peanuts in laboratory and animal studies.

The other category of treatments is immunotherapy, which is an effort to teach the immune system how to tolerate food allergens.

MARC RIEDL, M.D., is an assistant professor of medicine at the UCLA Medical Center. Reach him at (310) 794-1745 or mriedl@mednet.ucla.edu.





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