Food allergies can be triggered in infancy, a new review says. Here's how

Children face five major risk factors early in life that can set them up to develop food allergies, says a Canadian-led team of researchers who sifted through studies on 2.8 million participants in 40 countries, one of the largest reviews of its kind.

Those included infant eczema — a condition where the skin is dry, red and itchy — a family history of food allergy, delayed introduction of foods like peanuts or fish after 12 months, as well as parental migration, the team reported in a meta-analysis published in Monday's issue of JAMA Pediatrics.

Food allergies are rising worldwide and can cause life-threatening anaphylaxis. But predicting who will develop them remains a challenge. The review's authors believe the results could help lead to new prevention strategies. 

Dr. Derek Chu, the study's senior author and an assistant professor at McMaster University, sees patients with food allergies every day. He said one of the most common questions he gets from parents is whether they did anything wrong. The answer coming from the review is a reassuring one, he said.  

"Most ... food allergy is not driven by just one thing," said Chu, instead calling it a perfect storm. "There's been no major factor that mom or dad has done to make a major influence on risk."

For the review, Chu's team synthesized 190 studies to identify the strongest and most credible risk factors for developing food allergies, as well as more minor players. 

"We're now armed with the full catalogue of information about what's important in driving food allergy, and therefore it leads us naturally to how we can next prevent it," he said.

The five major risk factors the researchers flagged included: 

Parents and caregivers in Canada and the U.S. are recommended to give babies non-choking forms of foods containing common allergens like peanuts early, around six months of age. The advice was driven by a 2015 randomized trial, which found that doing so slashed the risk of high-risk infants developing allergies to the legume by age five.

For babies who tolerate allergy-provoking foods, current Canadian guidelines also stress continuing to offer the items a few times a week.

The same goes for other common allergenic foods, like fish, eggs and fruit. 

Besides delaying the introduction of these foods, the researchers found that atopic dermatitis or eczema early in life was another major risk factor for food allergy. 

"Very early atopic dermatitis and eczema should be directly addressed and rapidly," Chu said. 

The findings reinforce important concepts in food allergy, said Dr. Christine McCusker, a pediatric allergist and immunologist at the Montreal Children's Hospital, who was not involved in the paper.