MONDAY, Nov. 10 (HealthDay News) -- The number of U.S. children allergic to foods such as peanuts, milk and fish is rising rapidly.

At the same time, researchers are working on new approaches to treating these allergies, according to two reports to be presented Monday at the American College of Allergy, Asthma and Immunology's annual meeting, in Seattle.

An estimated 3 million children under 18 had a food allergy in 2007, an 18 percent increase since 1997, according to the U.S. Centers for Disease Control and Prevention.

"The problem is even more than numbers," said Dr. Sami L. Bahna, a professor of pediatrics and medicine and chief of allergy and immunology at Louisiana State University Health Sciences Center. "The severity of food allergies is going up."

There has been an increase in severe rashes; severe attacks of airway obstruction, called anaphylaxis; and intestinal problems, Bahna said.

What's more, the method of exposure that results in an allergic reaction is also changing, Bahna said. "People used to react by eating the food, but there are many people now that react by touching or smelling the food," he said.

Food allergies aren't the only allergies on the rise, Bahna said. "All the allergies are increasing -- asthma, hay fever, eczema," he said.

Several factors are contributing to the increase in allergies, the expert said. The first is the so-called "hygiene hypothesis," which holds that people in industrialized countries are living in increasingly sterile environments. As a result, their immune systems don't have to fight as many infections, so those systems can become hyperactive.

"When there is some degree of unhygienic conditions, the immune system from infancy adapts and develops to fight infection," Bahna said. "Cleanliness, antibiotics, whether they are needed or not, and vaccinations are allowing the immune system to develop as if 'I don't need you,' " he said.

Other reasons include the increased use of antacids among children, which prevents stomach acid from doing its job, and the increased use of multivitamins, which is associated with an increase in allergies, Bahna said.

Also, eating more highly allergenic foods such as fish, peanuts, tree nuts, milk, eggs and soy, as well as the increasing rates of childhood obesity, contribute to the rise in allergies, Bahna said. And, eating out hikes the risk for food allergies because you don't have total control over what you're eating. The ingredients in processed foods can also trigger allergic reactions, according to Bahna.

Allergic reactions can be severe -- even deadly. Current treatment is limited to avoidance of problematic foods and treating the symptoms of the reaction, Bahna said. But new treatments may be on the way.

Dr. Robert A. Wood, director of pediatric allergy and immunology at Johns Hopkins University School of Medicine, was scheduled to discuss potential new treatments for food allergies at the meeting on Monday. These include anti-IgE antibodies, a Chinese herbal remedy and immunotherapy.

Anti-IgE therapy disrupts the sequence of events that causes an allergic reaction. The treatment appears to work in about 75 percent of patients. Its drawbacks are that it must be given continuously and it does not work in the patient who is too allergic. There are also concerns about its safety and cost, Wood said.

A first clinical trial of the Chinese herbal formula FAHF-2 is also underway, Wood said. In experiments with mice, scientists found that peanut allergy was significantly reduced using this remedy.

The most promising approach appears to be immunotherapy, which is something Wood is involved in developing. In this treatment, tolerance is increased by giving patients increasing amounts of an allergen over time.

"This is sort of the allergy-shot model," he said, adding that several small studies have been promising. "We are cautiously optimistic that we are on the right path," he said.

Another presentation scheduled for the meeting looked at adults allergic to red meat. Researchers discovered that an IgE antibody to the carbohydrate galactose-a-1,3-galactose, which was found in patients who develop an allergy to beef, pork or lamb, seemed to explain the reaction.

Another study to be presented found that schools in one district in Greenville, S.C., had different action plans to deal with allergic reactions to food. The researchers found that fewer than 50 percent of the children with food allergies were on an action plan, however.

More information

To learn more about food allergies, visit the U.S. National Library of Medicine.