FOOD ALLERGIES
   Widely misunderstood 08.17.99

When the conversation turns to food allergies, you'll hear lots of folk wisdom: "Food allergies are common." "Many foods can cause allergic reactions." "Don't worry about food allergies — you just outgrow them." "Food allergies are never serious."

The facts contradict these common notions:

     

  • Only about 1 percent of Americans have genuine food allergies. Even so, about 20 percent believe that they have such allergies.

     

     

  • Ninety percent of food allergies involve just a few substances — proteins in cow's milk, egg whites, peanuts, wheat or soybeans.

     

     

  • It's true that children are 10 times as likely as adults to have food allergies. And by age 6, children usually outgrow allergies to milk, wheat and eggs. But some allergies — including those to nuts and shellfish — can persist for a lifetime.

     

     

  • Though uncommon, food allergies can lead to a life-threatening allergic response called anaphylaxis.

     

James T. Li, M.D., a specialist in allergies, asthma and immunology at Mayo Clinic, Rochester, Minn., spoke with Oasis about food allergies.

Oasis: What is a food allergy, and how does it differ from food intolerance or food poisoning?

Dr. Li: Some people can experience a host of troubling symptoms after eating certain foods. Among these symptoms are stomach upset, heartburn, hives, swelling, nasal congestion and diarrhea.

However, we must differentiate food allergies from other types of problems that foods can cause. From a medical standpoint, we use the term "food allergy" to mean a special type of immune system reaction to a food substance. This reaction involves allergy-producing antibodies that the body of a sensitized person makes. When these antibodies come into contact with an allergy-causing food, we see symptoms typical of an allergic reaction.

Though we see many people with a variety of problems associated with food, only a small proportion of those problems involve this allergic type of reaction. Many of the other types of symptoms that food can cause — heartburn, diarrhea, gas and more — don't involve food allergies at all.

Oasis: What are some common food allergies?

Dr. Li: Allergies to nuts, peanuts, shellfish and fish are common, especially in adults. Children can have these allergies, and they also may have allergies to milk, soy or wheat as well.

Oasis: What are common symptoms of food allergies?

Dr. Li: The symptoms due to a food allergy — when we use the term strictly — are fairly typical. These include:

     

  • Skin problems, including itching, hives or welts.

     

     

  • Swelling of the lips, hands or face.

     

     

  • Digestive symptoms such as nausea, cramps and diarrhea.

     

     

  • Respiratory symptoms, including wheezing or shortness of breath.

     

     

  • Lightheadedness, dizziness, fainting.

     

I would emphasize that when digestive symptoms occur alone, they do not necessarily mean that an allergic reaction is occurring.

The most serious consequences of a food allergy would include dizziness, lightheadedness and loss of consciousness.

Oasis: When do you need to call a doctor about food allergies?

Dr. Li: Consider getting medical attention in two different settings. The first is when the allergic reaction is actually occurring. Seek medical attention immediately when you notice breathing difficulties, dizziness or lightheadedness and swelling — especially swelling of the lips, tongue and upper airway. Certainly you'll need to call for emergency help when someone loses consciousness.

Second, call your health care provider if you have experienced symptoms of an allergic reaction to food. It's important to see a doctor who can help you discover the nature of the problem and how to deal with it. This kind of evaluation can occur during a scheduled office visit.

Oasis: How are food allergies diagnosed?

Dr. Li: Through a careful medical history, your doctor will try to obtain as many details as possible about the reaction, as well as details about your general health.

Usually your doctor also will conduct a physical examination. However, we don't expect any particular physical findings during an examination for food allergies unless you are having a reaction at the time of the exam. We do the examination mainly to exclude other types of medical problems.

We also do allergy skin testing or allergy blood tests that can help us make or exclude the diagnosis of food allergy. In the setting where a food allergy is suspected, positive allergy tests confirm the diagnosis. Negative (normal) skin test results would indicate that a food allergy is probably not the cause of the "reaction."

There are quite a few misconceptions about food allergies. The bottom line is that it's important for us to get the diagnosis right. Recommendations for treatment are based on that diagnosis. These allergies are often over-diagnosed by people having problems with food and even sometimes by their doctors.

Oasis: What are the main options for treating food allergies?

Dr. Li: Once we've made a diagnosis of food allergy and have identified the food causing the allergic reaction, the main piece of advice that we give people is to carefully avoid that food substance. This is easier said than done. Some food substances that cause allergic reactions, such as peanuts, are found in prepared foods sold in grocery stores or in restaurant-prepared meals. You wouldn't know about these substances unless you ask about them or read labels carefully.

Since avoiding the offending food is really the main issue, we have to make the right diagnosis. It's a shame for people who don't have a food allergy to fear an allergic reaction and to avoid a certain food when they could actually eat that food without problems.

For many people — especially those with more serious food allergies — we prescribe a kit for self-administered epinephrine (adrenaline). Epinephrine acts to help open the airway and maintain blood pressure in someone having a severe reaction. We want to make sure these people are equipped for an emergency and feel confident that they know how to deal with an allergic reaction should it occur.


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