One-third of babies naturally outgrow peanut allergies within a year

More than a third of babies who were previously diagnosed with peanut allergies safely tolerated them during subsequent testing. This suggests that a surprisingly high proportion of infants’ peanut allergies last less than one year, allowing them to be freed from a lifetime of food restriction and worry.

“Being able to identify those children early allows them to avoid an unnecessary allergy label and the burden of avoiding peanut,” says Tim Brettig at Murdoch Children’s Research Institute in Melbourne.

Since 2024, Australia has offered free treatment to all babies diagnosed with peanut allergy under the age of 12 months. The treatment, overseen by 10 public children’s hospitals across the country, involves feeding small but gradually increasing doses of peanut flour to allergic infants over two years to try to desensitise them, a strategy known as oral immunotherapy.

Before beginning the programme, babies are required to undergo an “oral food challenge” to confirm their allergy and assess its severity. It involves feeding them gradually escalating doses of peanut flour on a single day under medical supervision to see how much they can tolerate. The total given is 2500 milligrams, equivalent to two teaspoons of peanut butter. This is “above the threshold where we’d expect all children of this age to react if they have an allergy”, says Brettig, the medical lead of the programme.

However, of the first 778 babies with previously diagnosed peanut allergy who undertook the oral food challenge, 35 per cent did not react to any dose of the peanut flour. This was despite the fact they had previously developed rashes, swelling, hives or other signs of allergic reactions after consuming peanut-containing foods, and had skin prick or blood test results consistent with a peanut allergy.

“This was a surprising result for us – we expected a small proportion might pass the food challenge, but not 35 per cent,” says Brettig.

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The parents of these babies were given the good news that their child was no longer considered to have a peanut allergy and didn’t need to begin the oral immunotherapy programme. They were also assured that they could safely reintroduce peanut into their child’s diet at home.

The average time between the initial diagnosis of the peanut allergy and the oral food challenge was six months. It is unclear why a third of the infants stopped having reactions to peanut in this short window. “It might be that they had a transient allergy, where the immune system has an aberrant response to a food initially, but it doesn’t continue to occur,” says Brettig.

Previous research has found that roughly a third of children with peanut allergies naturally grow out of them by age 6, but this is the first time a high proportion of peanut allergies have been found to resolve on their own in infants.

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The finding will “make a huge difference” to the children whose allergy labels were removed, says Brettig, because they won’t have to spend their lives being burdened by restricted food choices, anxiety about accidental exposure to peanut and the need to carry emergency medication. It may also prevent them from developing a true peanut allergy down the track, since peanut avoidance in early life is known to increase the risk of allergies later on, he says.

The results also have wider implications for how peanut allergy is diagnosed and managed, says John Ziegler at the University of New South Wales, Sydney. Peanut allergy is commonly diagnosed based on clinical history and the results of skin prick or blood tests, usually without an oral food challenge.

Routinely conducting oral food challenges would identify those who don’t need require treatment, and thus be cost-effective, says Ziegler. “The study confirms the importance of confirmation of the diagnosis of peanut allergy before embarking on oral immunotherapy,” he says.

Due to the risk of severe reactions like anaphylaxis, such allergy treatments should only be conducted under medical supervision.

Source: A third of babies with peanut allergy grow out of it by 1 year old