Open this photo in gallery Megan Mudry feeds her one-year old daughter, Sophie peanut butter on toast as part of her lunch, at their home in Toronto on Jan. 23, 2019. Christopher Katsarov

Waiting years to feed babies foods that can trigger allergic reactions is not just outdated advice, it increases the risk they’ll develop allergies and has contributed to a dramatic increase in the number of children who can’t safely eat food such as peanuts and eggs.

The Canadian Paediatric Society (CPS) released new guidance on Thursday that, for the first time, actively encourages the parents of high-risk babies to start feeding their children common allergy-causing foods as soon as they are ready to eat solids.

The updated advice is a significant shift from the group’s last policy statement on the issue, published in 2013, which said only that there was no need to postpone the introduction of common allergenic foods beyond six months of age.

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And it’s a seismic shift from a discredited, nearly two-decades-old recommendation to avoid feeding peanuts to high-risk children until they turn 3.

Today, the evidence in favour of feeding babies peanuts and eggs early and often is robust enough that Canada’s pediatricians believe that the parents of high-risk children – namely those with severe eczema or a family history of allergies – could prevent food allergies by giving babies common allergens between four and six months of age.

For parents such as Jennifer Gerdts, the new guidance comes too late. She followed the old advice to delay the introduction of peanuts and other problem foods when her twin sons were born 17 years ago. They developed allergies to peanuts, some tree nuts, eggs, sesame and seafood, which, as Ms. Gerdts said, “made the simple act of eating very complicated.”

Now, the executive director of the non-profit group Food Allergy Canada, Ms. Gerdts said she is thrilled to see the CPS spreading the word about how to prevent food allergies.

“My twins would have fit into that category of medium-to-high risk because they had eczema as infants and there’s a family history of food allergies," she said. “So we would have been the perfect target for this new guidance.”

But not all doctors are offering up-to-date advice. The results of a survey of Canadian allergists, pediatricians and family doctors, published last summer, found that family physicians, “commonly recommended introduction of allergenic solids at age 1 year or more, whereas pediatricians and allergists were more aligned with current recommendations."

The confusion likely stems in part from the old recommendation that high-risk children avoid eggs until the age of 2 and peanuts and fish until the age of 3, which the American Academy of Pediatrics published in 2000. The Academy reversed course in 2008, saying there was no benefit to postponing problem foods beyond six months of age.

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In 2013, the CPS and the Canadian Society of Allergy and Clinical Immunology followed suit with a joint statement that offered similar advice, but noted that “the protective effect of early introduction of potentially allergenic foods (at four to six months of age) remains under investigation.”

Elissa Abrams, the president of CPS’s allergy section and the lead author of the new practice guidance, said that in the years since the group’s last official statement, “gold standard” evidence has emerged showing that high-risk children who start eating peanuts and, to a lesser extent, cooked eggs, earlier can largely prevent the development of food allergies.

“So we’ve shifted our position to actively introducing as opposed to not delaying, by about six months [of age], but not before four months of age,” Dr. Abrams said.

An important turning point came in 2015 with the publication of the Learning Early About Peanut, or LEAP study, a landmark British trial that found feeding high-risk babies puréed peanuts early and frequently reduced their risk of developing peanut allergies by as much as 80 per cent.

“It was very exciting because it suggested two things," said Gideon Lack, a pediatric allergy professor at Evelina Children’s Hospital at King’s College in London and the leader of the LEAP study. “It suggested, on the positive side, that now we had a new tool and a new strategy to prevent food allergies. It also potentially explains why we were having an increase in food allergies over the past few decades.”

The thinking, Dr. Abrams said, is that if you eat a common allergen as a baby, "you’re in effect teaching your body not to react to it.”

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The opposite seems to happen when young children are exposed to allergens, such as peanut dust, through the skin, which helps explain why babies with eczema are more prone to developing food allergies, she added. The new CPS document adds eczema to the list of factors that put children at high risk.

For Megan Mudry, 36, of Toronto, the change in emphasis is reassuring. She started putting dabs of peanut butter diluted with breast milk on her daughter Sophie’s tongue when the little girl was about six months old, even though Sophie was not obviously at risk of developing food allergies.

The pediatrician who cares for Sophie − who just celebrated her first birthday − was already an enthusiastic proponent of the early, but careful, introduction of foods that can trigger allergic reactions, Ms. Mudry said.

“Anything that reinforces something you did makes you feel very good as a parent," Ms. Mudry said. “So often you worry, ‘Have you made the right decision?' It feels very good to have that reinforced.”

With a report from Kathryn Blaze Baum