One-third of babies diagnosed with peanut allergy don't actually have one, study hints

A peanut allergy diagnosis in infancy can mean years of avoiding the food or undergoing treatments to build tolerance. But a recent study suggests that more than one-third of babies thought to have the allergy may stop reacting badly to peanuts within months of that diagnosis.

In an analysis published in The Journal of Allergy and Clinical Immunology: In Practice, researchers conducted supervised "food challenges" with infants diagnosed with a peanut allergy. These challenges involved giving the babies increasing amounts of peanut protein, with the intention of confirming whether they indeed had an allergy.

The team found that more than 1 in 3 infants who underwent the food challenge tolerated the peanut protein, meaning they didn't experience symptoms of an allergic reaction.

"This rate is much higher than we thought," study co-author Dr. Timothy Brettig, a pediatric allergist at the National Allergy Centre of Excellence in Australia, told Live Science.

Between April 2024 and October 2025, Brettig and colleagues retroactively reviewed the medical records of 1,275 infants who had been referred to Australian public hospitals after having a reaction to peanuts before their first birthday. These babies had first been assessed by allergy specialists at a median of 10 months of age.

For their initial diagnosis, the babies had to have a history of an allergic reaction to peanuts and show evidence of peanut sensitization on an allergy test. These tests included a skin-prick test, in which peanut extract is placed on the skin before it's lightly pricked, to check for a local reaction; and blood tests that detect antibodies against peanut proteins.

"Children under 1 year of age are an interesting group, as their immune system is still in rapid development and existing allergy tests may not reflect their allergic status well," said Dr. Alexandra Santos, a professor of pediatric allergy at King's College London who was not involved in the study. While these tests can hint that a child is sensitized to certain foods, they don't necessarily confirm that a baby will have an allergic reaction upon eating said food; the tests can also give false positives.

Of the 1,275 infants, 778 later underwent a food challenge roughly six months after their first recorded allergic reaction; at that point, their median age was 13 months old. They were given up to seven gradually increasing doses of peanut protein, ranging from 15 to 1,300 milligrams. These doses were given at 15-minute intervals while medical staff monitored the children for signs of an allergic reaction.

Nearly 35% of the participants — 271 kids — completed the challenge without reacting.

"This is an excellent article," said Dr. Drew Bird, a pediatric allergist at the University of Texas Southwestern Medical Center who was not involved in the study. "The take-home message is to strongly consider a supervised oral food challenge when an infant's peanut allergy diagnosis is uncertain."

Bird emphasized that these challenges should ideally be done before a child starts oral immunotherapy, a treatment in which patients regularly consume carefully measured amounts of the food they are allergic to. The dose is gradually increased under medical supervision, with the goal of helping the patient tolerate greater amounts of the allergen and reducing the risk of reactions from accidental exposure.

The starting dose is often determined through a similar oral food challenge to the one used in this study, though. So in theory, that challenge would help reveal whether the child needs treatment in the first place.

Bird cautioned that food challenges should be performed by a board-certified allergist-immunologist and an experienced allergy team in a setting equipped to treat anaphylaxis — a severe, potentially life-threatening allergic reaction.

In this study, 507 infants reacted during the food challenge, and of those, 61 developed anaphylaxis and were treated with epinephrine (the hormone in EpiPens).

"In an ideal world, with infinite resources," Santos said, "all patients except for those with a history of severe reactions would have a food challenge for diagnosis."

Because that is not the case, the families of infants whose allergy diagnosis is uncertain may be advised to avoid peanut products while they await a formal food challenge, she noted. But in the interim, they may miss an opportunity to help the child develop tolerance and, in turn, increase the risk that their allergy will persist.

Food challenges should be prioritized for infants whose allergy diagnoses are uncertain, she said. This would include babies who have low levels of peanut-specific antibodies in their blood or who show only small welts on skin-prick tests.