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.
New research out of the United States suggests that introducing peanuts to infants as young as four months old has helped to reduce the rate of peanut allergies in children by as much as 40 per cent.
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.”
Give babies peanut products early
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:
- Allergic dermatitis, also called eczema.
- Other allergic diseases early in life, such as allergic rhinitis or hay fever.
- A family history of food allergy or other allergic conditions.
- Early dry skin.
- Delayed timing of introducing food allergens.
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.
Eczema another risk factor
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.
Winter is a hard time for those with eczema, which can cause skin flaking, discolouration and discomfort. Dr. Shazma Mithani shares her tips to help manage your symptoms and keep your skin healthy during the dry, cold months.
For children with a genetic history, patients can apply creams to lower the risk of developing food allergies, McCusker said.
“It’s this focus on good skin care in very young infants and children. And by good skin care, sometimes it’s as simple as emollient therapies and/or removing soaps from the bath.”
Emollients are applied directly to the skin to soothe and hydrate it. When needed, eczema can also be treated with a variety of medications, she said.
The researchers also identified use of antibiotics during the first month of life as a major risk factor. However, Chu noted antibiotics remain important to treat severe infections in infants.
Chu said it’s possible that early antibiotics disrupt the body’s microbiome, referring to the bacteria in and on our bodies, which could factor into food allergies, but that needs to be studied further.
Other early life factors were not tied to a statistically higher risk of developing food allergies, according to the review, including low birth weight, post-term birth, partial breastfeeding, maternal diet and stress during pregnancy.
More trials needed, researchers say
The researchers acknowledged that more robust randomized trials, which take longer to do and are more costly than observational population studies, are still needed to tear apart any cause-and-effect relationships.
While they whittled down a huge number of papers and analyzed them as a group, McCusker said, the problem was the papers weren’t uniform, as they took place in different countries.
As Lucille Friesen, 17, of Anvil Island, B.C., wrote in a CBC First Person story, she was first diagnosed with anaphylactic peanut allergy at age two, followed by tree nut and soy allergies. Friesen said after a reaction landed her in the hospital, anxiety surrounding the allergies led to be extra careful at checking food ingredients.
Friesen’s mother said her eldest daughter had eczema as a baby. She’s also an example of someone who was introduced to allergy-provoking foods later than what guidelines for parents and caregivers now recommend.
“I can’t control where the science was,” Friesen told CBC News about the state of understanding around allergies when she was a baby.
“I’m just happy that it’s gotten to a place where it is now, that it can help other people. Maybe their quality of life could be better.”
