Contrary to the advice of some pediatricians, a new study suggests that waiting to introduce babies to cereal grains might not be a good idea if you want to prevent food allergies.

Babies who didn't eat grains until after they were 6 months old were more likely to develop wheat allergies, researchers report.

"We recommend introducing cereal grains between 4 and 6 months of age," said study co-author Dr. Jill Poole, an assistant professor of allergy, asthma and immunology at the University of Nebraska.

Poole initially expected the research would confirm the post-six-months recommendation.

For reasons that aren't entirely clear, food allergies are becoming more common among U.S. children, affecting an estimated 3 percent to 6 percent of all children, Poole said. Wheat allergies are among the top five allergies, which also include egg, milk, soy and peanut allergies.

There's controversy about when to expose babies to cereal grains, which are typically the first foods that babies eat after breast-feeding. Some specialists recommend cereal grains be introduced after 6 months of age, while others advise that they be given between 4 and 6 months.

For the new study, Poole -- who was working at the University of Colorado at the time of the research -- and her colleagues enrolled 1,612 children between 1993 and 2004 and followed them through the age of four.

Just one percent of the children -- 16 kids -- developed wheat allergies. But the study revealed that children who were first exposed to cereals (wheat, barley, rye and oats) after six months were 3.8 times more likely to have developed an allergy than those who first ate cereals earlier.

The risk of wheat allergy also went up by 1.6 times if the child was exposed to rice cereal after 6 months of age and by nearly four times if a parent or sibling had asthma, eczema, or hives, the researchers found.

The study results appear in the June issue of the journal Pediatrics.

Poole acknowledged that the number of children in the study who developed grain allergies was very small. But, she added, there was a "strong association" linking their allergies to their introduction to cereal grains.

Why would it matter when babies eat cereal grains for the first time? It seems to have something to do with the immune system, which overreacts in people with allergies, Poole said.

"Previously, we had thought if you delay giving foods to a child, it gives their immune system time to become mature and develop," she said.

But the study findings seem to debunk that theory, suggesting that perhaps the body's immune system "needs to see the food protein earlier to know it's not something harmful, and it shouldn't react to it," Poole said.

It may also be possible that children who begin eating grains later may eat more, potentially aggravating their immune systems, she said.

Dr. Kevin Murphy, clinical professor of pediatrics at the University of Nebraska, said genetic factors also appear to play a role in the development of allergies.

He called the new study "excellent," and said it confirms the advice of the American Academy of Pediatrics -- introduce cereal grains between 4 and 6 months of age.