Childhood allergies may be linked with gut bacteria, Canadian researchers believe

Several major childhood allergies may all stem from the community of bacteria living in a child’s gut, new research from the University of British Columbia and BC Children’s Hospital has found. 

Published in Nature Communications, the findings have identified gut microbiome features and early life influences that are associated with children developing any of four common allergies — eczema, asthma, food allergy and/or hay fever. 

Researchers hope their discoveries will lead to methods of predicting whether a child will develop allergies, and ways to prevent them from developing at all.

“Hundreds of millions of children worldwide suffer from allergies, including one in three children in Canada, and it’s important to understand why this is happening and how it can be prevented, said the study’s co-senior author Professor Stuart Turvey. 

The findings are significant because they are amongst the first to examine four pediatric allergies at once. While these allergic diseases each have unique symptoms, the Turvey lab was curious whether they might have a common origin linked to the infant gut microbiota composition.

“These are technically different diagnoses, each with their own list of symptoms, so most researchers tend to study them individually,” said fellow author Dr Charisse Petersen. “But when you look at what is going wrong at a cellular level, they actually have a lot in common.”

For the study, researchers examined clinical assessments from 1,115 children who were tracked from birth to five years of age. 

Roughly half of the children (523) had no evidence of allergies at any time, while more than half (592) were diagnosed with one or more allergic disorders by an expert physician. The researchers evaluated the children’s microbiomes from stool samples collected at clinical visits at three months and one year of age.

The stool samples revealed a bacterial signature that was associated with the children developing any of the four allergies by five years of age. The bacterial signature is a hallmark of dysbiosis, or an imbalanced gut microbiota, that likely resulted in a compromised intestinal lining and an elevated inflammatory response within the gut.

“Typically, our bodies tolerate the millions of bacteria living in our guts because they do so many good things for our health,” said first author Courtney Hoskinson. 

“Some of the ways we tolerate them are by keeping a strong barrier between them and our immune cells and by limiting inflammatory signals that would call those immune cells into action.

“We found a common breakdown in these mechanisms in babies prior to the development of allergies.”

Many factors can shape the infant gut microbiota, including diet, how a baby is born, where a baby lives, and exposure to antibiotics. Antibiotics may wipe out sensitive bacteria, while breastfeeding tends to replenish and provide necessary food for bacteria in the infant gut. 

The researchers examined how these types of influences affected the balance of gut microbiota and the development of allergies.

“There are a lot of potential insights from this robust analysis,” Dr Turvey said. 

“From these data we can see that factors such as antibiotic usage in the first year of life are more likely to result in later allergic disorders, while breastfeeding for the first six months is protective. This was universal to all the allergic disorders we studied.”

Researchers hope to leverage the findings to inform treatments that correct an imbalanced gut microbiota and could potentially prevent allergies from developing.

“Developing therapies that change these interactions during infancy may therefore prevent the development of all sorts of allergic diseases in childhood, which often last a lifetime,” Dr Turvey said.

Access the findings in full here.