Get the Facts Before You Pack Your Child's Lunch

By Kristina Hoffman Philpott, M.D.

At some point in their lives, most people have unpleasant reactions to certain foods. While many assume they are experiencing a food allergy, most of these reactions are the result of "food intolerances." Medical studies show that only 2 to 3 percent of infants and toddlers, and about 1 percent of adults, have clinically proven food allergies.

A true food allergy is an abnormal response to a food, triggered by the immune system. When the immune system overreacts to a food protein, an allergic reaction may result. Food intolerances differ from allergies in that they do not involve the immune system. It is important to identify true food allergies because these reactions can be severe and even life threatening.

• Food Allergies
• Food Intolerances
• Diagnosis
• Children with Allergies

Food Allergies

Immediate allergy symptoms to foods include itching; hives; swelling in the skin, mouth, airway or stomach lining; wheezing; airway spasms; vomiting; and/or anaphylactic shock. Most symptoms typically begin within a few minutes to hours after a person ingests the causative food.

The most common food allergens for American children are milk, eggs, peanuts, soybeans, wheat and fish. In adults with food allergies, the most common culprits are shellfish (such as shrimp, escargot, squid, crab and clams), peanuts, tree nuts (such as walnuts, pine nuts and almonds), fish and eggs.

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Food Intolerances

The most common form of food intolerance is lactose intolerance, which occurs in individuals with lactase deficiency. Lactase is an enzyme made by the cells lining the stomach. It is responsible for breaking down lactose, the simple sugar found in dairy products. The symptoms of lactose intolerance are gas, bloating, abdominal pain and sometimes diarrhea.

Some food intolerances are fairly obvious, such as spicy foods causing heartburn and a runny nose, or high-fat foods taking longer to digest and causing stomach cramps. Another, lesser-known food intolerance involves foods that naturally contain "histamine-like" substances, causing itching and hives. These food culprits tend to be certain cheeses, wines and certain types of fish. People prone to migraines may be more susceptible to this type of food intolerance.
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Diagnosis

To distinguish a food allergy from a food intolerance, it is helpful for an individual to keep a diet diary that tracks details about past reactions, including type of food, portion size, timing of symptoms, treatments given and other factors. This information helps a physician properly diagnose the problem.

In some cases, even a detailed history is not enough to pinpoint the diagnosis. In this case, a physician may request diagnostic tests and/or refer a patient to an allergist or gastroenterologist. An allergy specialist may recommend skin-prick tests or blood tests to determine allergic reactivity.
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Children with Allergies

While it is more common for children to have food allergies, the good news is that 85 percent of childhood allergies - to foods such as milk, soy or eggs - disappear by age 3. Unfortunately this is not true of peanut, tree nut, shellfish and fish allergies, which generally persist into adulthood.

Food allergies can be prevented or delayed in infants born into allergy-prone families. Exclusive breastfeeding for at least six months, if possible, is recommended, with maternal avoidance of foods containing peanuts, nuts, eggs and seafood. Delayed introduction of these and other highly allergenic foods in the child's diet is also recommended until he or she is older.

While many children and adults will experience food allergies or intolerances during their lifetimes, there are many ways to manage the problem in partnership with a physician.

Kristina Hoffman Philpott, M.D., specializes in allergy and immunology at the Palo Alto Medical Foundation. This article was originally published in the Redwood Shores Pilot.

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