Food allergies.

One third of adults believe they have a food allergy, but probably only 2 percent actually do.

My husband is a pediatrician and I'm a nutritionist. Sometimes it takes both of us to solve a patient's problem. Like Megan's. A tiny 1-year-old, she ranked at the bottom of the growth chart, was highly allergic to cow's milk, and didn't seem very interested in eating. She couldn't tolerate any food containing milk, and it was a challenge to find things she could and would eat. Over a period of months her mother and I tried many options, while my husband treated her medically.

Megan's case is typical of truly allergic people. I say "truly allergic" because even though one third of adults believe they have a food allergy, probably only 2 percent actually do. Five percent of children are so diagnosed, but fortunately their allergies are often outgrown.

Allergic people are born with an immune system that overreacts to normally harmless food components. They make antibodies (IgE) that attack antigens (usually proteins) in the offending foods.

Even after the allergic reaction is over, millions of IgE cells remain in their bodies. These cells congregate in the skin, lungs, and gastrointestinal tract, ready to cause trouble the next time the food is eaten--a rash, itching, swelling, trouble breathing, or vomiting and diarrhea. Rarely is an allergic reaction (anaphylaxis) fatal. Reactions can occur almost immediately or several hours after the food is eaten.

Food allergy tests. If you suspect a food allergy, what should you do? First make an appointment with your physician and meanwhile avoid the suspected food. It's important to have a medical evaluation because many problems other than allergies can cause similar symptoms. Ruling out other possibilities can be done through a physical examination and appropriate tests.

The doctor may ask you to keep a diary for a period of time, recording when and what you eat and your symptoms. If it appears likely that the symptoms are related to a specific food, an elimination of that food may be tried. If the symptoms disappear after several weeks and reappear when the food is eaten again, an allergy is likely.

More specific tests include skin tests, as well as the radiollergosorbent (RAST) or enzyme-linked immunosorbent assay (ELISA) blood tests.

Skin testing consists of applying a diluted extract of the suspected food to the skin and then scratching or puncturing the skin. If the skin reacts within 15 minutes by developing a bump with redness, similar to a mosquito bite, an allergy to that food is likely. The blood tests give similar information.

Cytotoxic testing and symptom provocation testing involving oral administration or injection of food extracts are unreliable and not recommended.

Living with the allergy. Once the diagnosis is made, the next step is to devise a game plan for living with the allergy. I feel like an expert in this area because my husband is highly allergic to milk, so I'm constantly adjusting recipes. He reacts to even small amounts of milk products.

Some people are fortunate enough to tolerate the offending food to a limited extent, making life a lot easier. But in the worst-case scenario, finding substitues and completely avoiding the foods are essential. This means reading labels religiously.

The most common food allergies are to milk, eggs, fish, shellfish, soy, wheat, and nuts. Following an elimination diet is tough, but there is one ray of hope from recent research. One study found that a third of allergic adults and older children who completely avoided the problem food for one to two years "outgrew" their allergies. They were no longer sensitive!

Since allergic reactions can occasionally be fatal, a person who has severe reactions should be prepared in case of accidentally eating the problem food. Learning how to give an injection of epinephrine (adrenaline) and always carrying a syringe filled with the medication could be lifesaving. For milder reactions oral anthistamines may be helpful. A Medic Alert bracelet could save valuable time for medical personnel should the allergic person be found unconscious. Unfortunately there aren't any drugs to cure food allergies. The desensitization shots, helpful for allergies to pollens, aren't effective for food allergies and may be dangerous.

Food intolerances. Sometimes what appears to be a food allergy is really a food intolerance. Allergic reactions are caused by the immune system, but similar symptoms can be a result of problems in digesting certain foods. For instance, lactose intolerance causes nausea, gas, cramping, and diarrhea after drinking milk or eating milk products. This problem is common among all ethnic groups except Northern Europeans, and even some of them have it.

Lactose intolerance often develops in early adulthood. The body stops making enough of the enzyme, lactase, that digests the lactose in milk. The undigested lactose causes the diarrhea and cramping. Grocery stores and pharmacies carry various commerical products for people with lactose intolerance. Other problem substances include sulfites and MSG. Sulfites are sometimes added to preserve foods or to prevent their discoloration. Only a tiny portion of the population is sensitive to sulfites, but the reactions can be fatal. Sulfites are listed on the label when used and are no longer permitted on fresh fruits and vegetables (except potatoes).

MSG (monosodium glutamate) is considered safe. The small number of people who react to it are only mildly affected for a short time.

The sugar substitute aspartame is believed to be nonallergenic.

Trying to work around an allergy can be frustrating, but sometimes rewarding. Like the evening when my husband came home and said, "Megan and her mother came in today. Megan's doing so well and her mother is so pleased. She doesn't know who did it, but she thinks that one of us is really smart!"