More than 1 in 3 babies diagnosed with peanut allergy ate peanut in a supervised hospital test without reacting

Of 778 Australian infants who carried a peanut allergy diagnosis and later sat through a supervised oral food challenge in a hospital, 271 ate the peanut without reacting. That works out to nearly 35%, or more than 1 in 3. The finding comes from a record review led by pediatric allergist T. W. Brettig of the National Allergy Centre of Excellence.

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The infants had all been referred to public hospitals after a reaction to peanut before their first birthday. Allergy specialists first saw them at a median age of 10 months, and the challenge came about six months after that initial reaction.

271 of 778 infants who passed the challenge

Brettig and colleagues, writing in The Journal of Allergy and Clinical Immunology: In Practice, reviewed medical records from April 2024 to October 2025 covering 1,275 referred infants. A diagnosis required a history of reacting to peanut plus evidence of sensitization, meaning a positive skin-prick test or blood antibody test. Of the 1,275, 778 went on to a supervised challenge at a median age of 13 months.

Staff gave up to seven increasing doses of peanut protein, from 15 to 1,300 milligrams, spaced 15 minutes apart while watching for symptoms. As Live Science reported, 507 infants reacted, including 61 who developed anaphylaxis and received epinephrine. The other 271 tolerated every dose. Brettig said the proportion was far higher than the team had expected. The arithmetic matters for the claim in the paper: 271 passes out of 778 attempts is 34.8%, so “more than 1 in 3” holds, while the reactions were not trivial, since roughly 1 in 13 of the challenged infants (61 of 778) needed epinephrine for anaphylaxis. The full text is listed on the publisher’s record.

Sensitization on a test is not the same as an allergy

Skin-prick and blood tests detect antibodies to peanut protein. A child can carry those antibodies and still eat peanut safely, which is why the tests generate false positives. In infants the problem may be sharper: Alexandra Santos of King’s College London, who was not part of the study, noted that children under one have developing immune systems and that existing tests may not reflect their true status well.

The stakes are practical. Families told to avoid peanut may wait months or years before anyone retests, and avoidance during that stretch can delay the development of tolerance. The Australian program the study evaluated feeds into peanut oral immunotherapy, a treatment that raises a child’s tolerated dose, and the paper argues a challenge should come before that therapy starts so that infants who never needed it are not enrolled. The paper’s own wording argues that an oral food challenge is required for accurate diagnosis before oral immunotherapy in infants. A wrong label carries a cost in either direction: an unnecessary restriction on one side, an unrecognized danger on the other.

Santos said that with unlimited resources, every patient except those with a history of severe reactions would have a food challenge to confirm the diagnosis. Drew Bird of UT Southwestern Medical Center, also not involved, advised clinicians to strongly consider a supervised oral food challenge when an infant’s diagnosis is uncertain.

Limits of a retrospective review in one health system

The result applies to the 778 infants who were challenged, not to all 1,275 referred. The article does not explain why the other 497 never had a challenge, and if those infants were deliberately skipped because their tests looked more convincing, the true tolerance rate among all diagnosed babies could be lower. A retrospective design, drawn from one country’s public hospitals, also cannot show how the same infants would have fared under a different diagnostic approach. Live Science’s account of the paper does not say how many families kept peanut out of the diet while waiting for the six-month challenge, a gap that matters because avoidance can delay tolerance. Challenges, the outlet notes, should be run by a board-certified allergist-immunologist in a setting that can treat anaphylaxis, which narrows where the findings can be put to use.

Existing U.S. guidance is cautious about when and how to test. The 2017 addendum guidelines from a National Institute of Allergy and Infectious Diseases expert panel chaired by Joshua Boyce advise introducing peanut-containing food as early as 4 to 6 months in infants with severe eczema or egg allergy, after strongly considering peanut-specific IgE or skin-prick testing. A skin wheal of 3 to 7 millimeters calls for a supervised feeding or graded challenge at a specialist site, and the clinician summary says such a challenge belongs in the hands of a specialist equipped to treat reactions.

That specialist requirement is the constraint Santos pointed to: challenges need staff time, monitoring and emergency capacity. She suggested prioritizing infants with low peanut-specific antibody levels or small skin-test welts, where a negative outcome is most likely. Whether public systems can build that capacity, and whether a prospective trial would reproduce the 35% rate, are questions the Brettig team’s data raise but cannot answer.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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