Peanuts are among the most popular snack foods in the United States.

Millions of American children are raised on peanut butter and jelly sandwiches. PB&Js, as we like to call them, are found in children’s lunchboxes across the country. Or at least they used to be.

Now, many school officials ban peanuts or any products containing peanuts from school property. About 2 percent of U.S. schoolchildren will have an allergic reaction to peanuts. And that number is growing.

People allergic to peanuts can develop skin conditions or watery eyes. Children with a peanut allergy can develop a skin condition called eczema. Some reactions are so severe they can result in death.

So far, doctors have advised parents against serving peanut-containing foods to children under the age of 3. But a 2015 British study found that waiting too long most likely is partly to blame for the peanut allergy problem.

Anthony Fauci is head of America’s National Institute of Allergy and Infectious Diseases. Dr. Fauci spoke to VOA on Skype. He notes that in Israel, people have a tradition of feeding peanuts to babies.

He says the percentage of Israeli children with a peanut allergy is much lower than the rate among Jewish children living in England.

"It was observed that in Israel -- where they have a custom of feeding peanut-based foods to babies, infants, within the first few months of life -- that when you, in fact, compare the incidence of peanut allergy among the Israeli children compared to comparable Jewish children living in England, the incidence of peanut allergy was more than 80 percent decreased among the Israeli kids as opposed to the kids who are living in England."

Dr. Fauci says this finding is very important. It means that babies have a natural mechanism that can be trained not to react negatively to peanuts. That mechanism may turn off as the baby reaches the age of 1.

He says a team of experts have agreed on a new guidance for U.S. pediatricians who specialize in children's allergies.

Fauci calls giving children peanuts a way of “challenging” their bodies. He thinks it could be done safely with some boys and girls, but not with others.

"If the child has a history of severe eczema or egg allergy, that in the first 4 to 6 months of life, that you should bring the child to an allergy specialist who can do a skin test or a blood test to determine if the child does have an underlying allergy to peanuts.

Because if they do, you are going to want to refrain from challenging that child. Whereas if they don't, then it would be safe to challenge the child and feed them peanuts at 4 to 6 months."

If the child has moderate eczema and has a mild reaction to eggs, the doctor is likely to suggest that that child be fed peanut-containing foods at the age of 6 months. That child may need no allergy tests either.

Children who have no allergies or family history of allergies can be given peanuts at any age.