Approximately 2%-3% of Americans are allergic to peanuts. Previous research studies have suggested that introduction of the peanut in the first year of life to infants highly likely to develop a peanut allergy reduces that risk by approximately 80%. However, the best method to safely do this is unclear. Now, a Johns Hopkins Medicine research team has conducted a study that shows which babies are most at risk for peanut allergy and which tests are best for diagnosing them. 

The team’s findings were reported in two papers in the Jan. 19, 2021, issue of the Journal of Allergy and Clinical Immunology. One paper identifies the likelihood of  babies developing a peanut allergy, finding that older infants and ones with moderate-to-severe eczema are most at risk. The other paper compares diagnostic tests for detecting peanut allergy.

“Early introduction of peanut is important to prevent peanut allergy,” says Corinne Keet, M.D., Ph.D., associate professor of pediatrics at the Johns Hopkins University School of Medicine. “Current recommendations are that infants with severe eczema be exposed to peanuts early in the first year of life, but also that they get testing before introducing to make sure that they are not already allergic.”

“We wanted to know what the real risk for peanut allergy was in this group, and in other potential risk groups, and what tests would be best to use for screening,” she explains.

Researchers enrolled 321 children, ages 4 months to 11 months, who had at least one of the following risk factors: a family history of peanut allergy, moderate or severe eczema, or another food allergy other than peanut. The average age of the infants was 7 months and 58% were males. As for racial and ethnic demographics, 74% were identified as white, 8% as Black, 7% as Asian and 12% as multiracial or another racial background. Of the 321, 195 had eczema, 201 had a sibling or parent with a peanut allergy and 59 had a personal history of a food allergy other than peanut. Infants who were enrolled had a skin prick test and blood testing for peanut allergy, and were fed peanuts under observation.

The researchers found that 18% of the infants with moderate to severe eczema were allergic before introducing peanut. They found that risk increased with the severity of eczema, and also increased with each month between 4 months and 11 months of age.

This, say the researchers, suggests that introducing infants with severe eczema to peanuts before they reach the age of 6 months is necessary to effectively prevent the allergy. In contrast, they found that only 1% of the infants who had siblings or parents with a peanut allergy but who did not have eczema had peanut allergy when evaluated. Therefore, the researchers suggest that these infants do not need testing before starting to eat peanut products.

When comparing tests to predict the risk for developing a peanut allergy, the researchers found that the standard tests for peanut allergy — the peanut-specific IgE (looking for antibodies formed in response to the entire peanut) and the peanut skin prick test — had high false positive rates. A more recent test that detects IgE specific to one component of the peanut called Ara h 2, rather than the whole peanut, provided a more accurate diagnosis. Current guidelines for diagnosing peanut allergies in infants may need to be modified to reflect these findings, the researchers say.

The researchers conclude that parents of infants with significant eczema should discuss peanut introduction with their pediatricians, with the goal of getting the child exposed to peanut-containing foods before 6 months of age.

Ongoing research by the Johns Hopkins Medicine team involves finding ways to deal with peanut allergies already developed in children, including treatments such as medications and immunotherapy. Clinical trials are planned, including one that will study children with multiple food allergies in order to test methods for treating the allergies all at once.

Keet is available for interviews.