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THURSDAY, July 10 (HealthDayNews) -- Children with mild peanut allergies have at least even odds they'll outgrow the problem, but a few who do may experience a rerun of the reactions.

So says a new study that followed 80 children with a history of peanut allergies, considered one of the most severe food reactions. Overall, the scientists say, between 20 percent and 25 percent of kids with peanut allergies will ultimately shed the affliction.

"It's better than we used to think," says research leader Dr. Robert Wood, a pediatrician and allergy expert at the Johns Hopkins Children's Center in Baltimore.

In a different study, Wood and his colleagues also found they can identify who is likely to outgrow their peanut allergy by looking at their immune system's reaction to small bits of peanut protein.

"It turns out that if you are reacting to a certain portion of the protein you have a far lesser chance of outgrowing it. But if it's a different part, you have a much better chance," Wood says.

Eventually, doctors could measure that reaction with a simple blood test. "The same is likely to be done with milk and egg allergies, where we're finding the same kinds of differences," he adds.

Dr. Hugh Sampson, an allergist at the Mount Sinai School of Medicine in New York City and a co-author of the peanut protein study, says such a test for peanuts could avoid up to 90 percent of future allergy tests to determine which children have outgrown the condition. These tests can provoke unpleasant and possibly dangerous reactions.

The studies appear in July issue of the Journal of Allergy and Clinical Immunology, which this month is devoted to peanut allergy research. Researchers held a press briefing Thursday to discuss the findings.

An estimated 1.5 million Americans are allergic to peanuts, and each year nearly 100 die after contact with them, according to the Food Allergy and Anaphylaxis Network. For some people, as little as 1/1,000th of a peanut can trigger a deadly reaction.

Until only recently, doctors believed peanut allergies were lifelong affairs. But a recent study by Wood's group showed that as many as 20 percent of toddlers allergic to peanuts grow tolerant to them by the time they enter school.

The latest study extends that work. Wood and his colleagues followed 80 children, aged 4 to 14, with a history of peanut allergy. All had blood levels of IgE -- the immune molecule that binds to peanut proteins -- of 5 kilounits per liter of blood, and many had much less of the antibody.

When tested again with a bit of peanut protein, 55 percent of the children passed the test, suffering no allergic reaction. That rate was even higher among those whose IgE levels were 2 kilounits or less.

Although 55 percent of children in the new study outgrew their allergy to peanuts, as many as three-quarters of those who reacted to the food have IgE levels above 5, Wood says. The study found that 23 percent of peanut allergy sufferers overall would lose their sensitivity with time.

"The incidence and prevalence of peanut allergy is increasing markedly," says Dr. Donald Leung, an allergy specialist at National Jewish Medical and Research Center in Denver. Peanut allergies account for roughly half of the 200-odd fatal food reactions in the United States each year, he adds.

While serious allergic reactions can be avoided with a prompt shot of epinephrine, eight in 10 people who die of food allergies never receive proper instruction in how to self-administer the injection, Leung says.

Researchers would like to prevent food allergies from occurring, rather than treat them in their throes. Sampson is helping lead an effort at Mount Sinai to create a peanut allergy vaccine, a gel-filled suppository that would activate a regulatory element of the immune system.

Work in rodents has been successful, he says, and the group hopes to test the vaccine in humans as early as next year.

More information

Check out the Food Allergy & Anaphylaxis Network or the American Academy of Allergy Asthma & Immunology.