When food is the enemy

Five things to know if you suspect a food allergy

By Catherine Bennett Dunster

January 24, 2008

Editor’s note: Catherine Bennett Dunster wrote the Health+Food column from June 2007 to April 2008.

“How do I know if I really have a food allergy?”

Yours is one of many allergy comments and questions we’ve received since Curt Ellis, of the film “King Corn,” tossed us the corn challenge. Food allergies are fraught with misunderstandings. Here are five things you should know if you’re concerned about food allergies.

First, not everyone has a food allergy.

Talk to a handful of family and friends, and you might think everyone is allergic to one food or another. But in truth, only six to eight percent of children and two to four percent of adults in the United States suffer from food allergies. Unfortunately, these figures are on the rise, and there are a couple of theories why.

According to Wesley Burks, the chief of pediatric allergy and immunology at Duke University, one theory is that unrecognized allergens may lurk in the processed foods that are increasingly common in the Western diet and may heighten sensitivity to peanuts and other allergens.

The second theory — referred to as the “hygiene hypothesis” — suggests that with our heavy use of antibacterial products, as well as what some consider an obsession with hygiene, children aren’t as frequently exposed to microbes and allergens that would train their developing immune systems.

Cooked shrimp: Tasty treat, or sudden death?

Though any food can cause a food allergy, there are eight common food allergens that are responsible for more than 90 percent of serious allergic reactions to food: peanuts, tree nuts (cashews, walnuts, almonds, pistachios, and pecans), eggs, dairy, wheat, soy, fish, and shellfish (such as crab and shrimp).

Second, food intolerances are different than food allergies.

An intolerance to food is any unfavorable reaction to food that does not involve the immune system. Lactose intolerance is an excellent example. Somebody with lactose intolerance lacks the enzyme responsible for digesting the milk sugar called lactose. When this person consumes milk or dairy products, he or she experiences unpleasant gastrointestinal symptoms including bloating, flatulence, and abdominal pain.

A true food allergy occurs when the body’s immune system reacts to a certain component (usually a protein) in a food. Reactions to an allergen occur within minutes — and not more than an hour or two — after consumption. When a reaction occurs, the body creates immunoglobulin E (IgE) antibodies to the food, and the immune system releases vast amounts of chemicals to protect the body.

These chemicals, in turn, trigger allergic symptoms that can affect the respiratory tract, the cardiovascular system, the skin, and the gastrointestinal tract. Symptoms include hives or an itchy rash, a tingling sensation in the mouth, abdominal cramps, vomiting, diarrhea, difficulty breathing, and swelling of the eyes, lips and tongue. In extreme allergic reactions, heart failure, circulatory collapse, and death can result. Food allergy symptoms will occur each and every time you ingest the allergen, though these symptoms can vary in severity.

Having a food intolerance can result in some nasty symptoms. But having a food allergy means the symptoms can be both undesirable and life-threatening. It’s important to know the difference!

Third, diagnosis can be challenging.

First and foremost, if you suspect a food allergy, make a note of any symptoms you experience, how long after eating they occur, and which food (or foods) you suspect to be the culprit. A food diary listing all of the foods you consume for one to two weeks is an excellent way to do this.

Next, armed with your food diary, consult your primary health-care provider or board-certified allergist, who will likely employ one of two commonly used tests: the skin-prick test or a blood test such as the RAST, CAP-RAST, CAP-ELISA, or ImmunoCap.

The skin-prick test can be done right in the doctor’s office and therefore is generally the cheaper option. The doctor places a drop of the suspected substance on your forearm or back and pricks the skin with an instrument akin to a needle, allowing a minute amount to enter the skin. If you are allergic to the substance, a swelling forms at the prick site within about 15 minutes.

With the RAST, a blood sample is sent to a medical laboratory, and tests are done with specific foods to determine whether you have IgE antibodies to that food.

Positive results to either of these tests, combined with your history of symptoms, will determine whether a food allergy exists or not.

Fourth, strictly avoiding the allergen is the only way to avoid a reaction.

Even the most trivial amounts of an allergy-causing food must be avoided to fend off reactions. Though most people eventually outgrow their food allergies, peanuts, nuts, fish, and shellfish are generally considered lifelong allergies. To help maintain control over a food allergy, reading food-ingredient labels is imperative and may save your life. If a label contains terms that are unfamiliar to you, call the manufacturer directly with questions or avoid that food altogether.

Finally, there is unfortunately no cure for food allergies.

However, some research looks promising in this area. After identifying the predominant allergy-triggering proteins in peanuts, Duke University’s Wesley Burks and his colleagues are working toward a peanut-allergy vaccine, which would help desensitize sufferers to peanuts. Though a ways off, allergists and their patients are quite excited about the prospect of a vaccination in the future.

Of course, if you experience severe symptoms, seek medical advice immediately. Otherwise, avoid randomly deleting foods from your diet (which can cause an inadequately balanced diet and lead to nutritional deficiencies) until the cause of your symptoms can be determined.

For additional information and support, I heartily recommend two excellent sources: The Food Allergy and Anaphylaxis Network and The Food Allergy Initiative. Both are invaluable, scientifically based organizations with easy-to-navigate websites.

Catherine Bennett Dunster is a registered dietitian and a former instructor at Oregon Health and Science University. She lives with her husband and two children in Portland, Oregon.

Please send your nutrition questions to Health+Food@culinate.com.