After a 10-year effort, the nation's major allergy organizations have agreed on how best to diagnose and manage food allergy.

The new "practice parameters," from a panel of allergy experts, are a state-of-the-art guide on how to detect and treat food allergy.

Food allergies are common -- and commonly misunderstood by doctors as well as patients, says panel co-chairman Jay M. Portnoy, MD, who is chief of allergy, asthma, and immunology at Children's Mercy Hospital in Kansas City, Mo., and vice president of the American College of Allergy, Asthma & Immunology.

"I see patients all the time who go to a doctor, skin-test positive for lots of different foods, and are advised to avoid all of these foods," Portnoy tells WebMD. "It makes their life miserable. And it turns out they are not truly allergic to all these foods after all."

Portnoy's complaint rings true with patient advocate Anne Muñoz-Furlong, founder and CEO of The Food Allergy & Anaphylaxis Network (FAAN).

"Some parents never suspect food allergies until their child ends up at the emergency room -- where they might be told it is a food allergy, or they might not," Muñoz-Furlong tells WebMD. "Or if the child first has mild symptoms, like eczema, they may not realize it is a food allergy. And then the entire family suffers until a diagnosis is made and the food is eliminated from the diet."

The new guidelines appear in the March issue of the Annals of Allergy, Asthma & Immunology.

The Most Common Food Allergies

Food allergies occur when a sensitive person eats, inhales, or comes into contact with even tiny amounts of foods or food additives. These allergic reactions can be very mild or may be life-threatening.

Food allergies are becoming more and more common. There has been an increase in severe food allergy cases in the last 10 years, mostly driven by peanut and tree nut allergies.

In children, the most common food allergies are:

--Cow's milk

--Hen's eggs

--Peanuts

--Tree nuts

--Soybeans

--Wheat

In adults, the most common food allergies are:

--Peanuts

--Tree nuts

--Fish

--Crustaceans (such as shrimp, crabs, and lobster)

--Mollusks (such as clams, oysters, and mussels)

--Fruits

--Vegetables

In children, the foods most likely to cause severe allergic reactions -- anaphylaxis -- are peanuts, other legumes, tree nuts, fish, shellfish, milk, and eggs.

In adults, the foods most likely to cause anaphylaxis are peanuts, tree nuts, fish, and shellfish.

Symptoms tend to occur just after eating. They may include reddening of the skin, hives, itchy skin, swollen lips or eyelids, tightness of the throat, wheezing, difficulty breathing, coughing, vomiting, or diarrhea.

If you or your child has symptoms soon after eating, it's time to get tested.

Allergy Testing

Testing is the most controversial aspect of food allergy treatment. Just getting a skin test or a blood test isn't enough, says guidelines chief editor John J. Oppenheimer, MD, of the UMD-NJ New Jersey Medical School in New Brunswick.

"My pet peeve is now we have these blood tests and skin tests but without a patient's or a parent's help, they may provide misinformation," Oppenheimer tells WebMD. "So when a reaction occurs, try to figure out what you or your child ate over the last several hours. And then tell the doctor your story. Doing testing blindly can result in more problems than it solves."

The problem is that tests for food allergy are very sensitive. This means that if you do have a food allergy, the tests are very likely to catch it. But the tests aren't very specific. This means that the tests often are positive when there's no food allergy.

"People get 100 tests, and many are false positives and they end up chasing their tails," Oppenheimer says.

The new guidelines help doctors use food allergy tests in the best possible way. And when used properly, Portnoy says, testing works.

"Don't just assume you have a food allergy. If you suspect one, get it confirmed," Portnoy says. "You have to make sure you really are allergic. I have seen people with nutritional problems due to avoiding foods not really allergic to."

It's very rare for a person to be allergic to more than one or two foods, Oppenheimer and Portnoy say. So if testing is used to confirm or reject suspect foods, it is more likely to give meaningful results.

Managing Allergies

Once a food allergy is found, Muñoz-Furlong says, the real work begins.

"You have to learn how to manage the allergy on a day-to-day basis," she says.

FAAN has a web site -- which both Oppenheimer and Portnoy recommend -- to help parents and adult patients manage their food allergies.

"Unfortunately, the only treatment we have is avoidance," Oppenheimer says. "But I have several suggestions that help. One is to wear a medical alert bracelet or necklace. And for restaurants, I am big fan of giving the server a card that shows what you are allergic to, and having the chef sign the card to make sure you aren't given anything you're allergic to."

Outgrowing Food Allergy

The new guidelines stress repeated testing to see whether a food allergy fades over time.

Many children with food allergies become tolerant to those foods over time. This is most likely to happen with allergies to cow's milk, hen's eggs, wheat, and soybeans. It's least likely to happen with peanut, tree-nut, and seafood allergies.

"So it's necessary to recheck patients to see if they are still allergic," Portnoy says.

When a person becomes less sensitive to a food to which they have been allergic, doctors call it "tolerance." It's hoped that scientists will one day learn how tolerance develops -- and how to induce tolerance.

"Why tolerance occurs is the million-dollar question in food allergy," Oppenheimer says. "We are working on it."

By Daniel J. DeNoon, reviewed by Brunilda Nazario, MD

SOURCES: Chapman, J.A. Annals of Allergy, Asthma & Immunology, March 2006; vol 96: pp S1-S68. FAAN web site, foodallergy.org. John J. Oppenheimer, MD, clinical associate professor, New Jersey Medical School, New Brunswick. Jay M. Portnoy, MD, chief of allergy, asthma, and immunology, Children's Mercy Hospital, Kansas City, Mo.; vice president, American College of Allergy, Asthma & Immunology. Anne Muñoz-Furlong, founder and CEO, The Food Allergy & Anaphylaxis Network (FAAN).