According to a new study led by experts at the University of British Columbia and BC Children’s Hospital, some common childhood allergies may be caused by the bacterial community that lives in our gut.
The study, published in Nature Communications, reveals gut microbiome traits and early life variables that are linked to children having one of four common allergies: eczema, asthma, food allergy, or hay fever. The discoveries could lead to methods for predicting whether or not a youngster would develop allergies, as well as ways to prevent them altogether.
“We’re seeing more and more children and families seeking help at the emergency department due to allergies,” said Dr. Stuart Turvey, professor in the department of pediatrics at UBC and an investigator at BC Children’s Hospital Research Institute, and co-senior author on the study. “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.”
These are technically different diagnoses, each with their own list of symptoms, so most researchers tend to study them individually. But when you look at what is going wrong at a cellular level, they actually have a lot in common.
Dr. Charisse Petersen
The study is one of the first to examine four distinct school-aged 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,” says Dr. Charisse Petersen, co-senior author on the paper and postdoctoral fellow in the Turvey lab. “But when you look at what is going wrong at a cellular level, they actually have a lot in common.”
The researchers looked at clinical assessments from 1,115 children who were tracked from birth to age five. Approximately half of the children (523) showed no signs of allergies at any time, whereas more than half (592) were diagnosed with one or more allergic illnesses by an experienced physician. The researchers assessed the children’s microbiomes using stool samples collected during 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. 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,” says Courtney Hoskinson, a Ph.D. candidate at UBC and first author on the paper. “We found a common breakdown in these mechanisms in babies prior to the development of allergies.”
Many factors can shape the infant’s gut microbiota, including diet, how we are born, where we live, and our exposure to antibiotics. For example, antibiotics may wipe out sensitive bacteria, while breastfeeding tends to replenish and provide necessary food for bacteria in the infant’s 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,” says Dr. Turvey. “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.”
The researchers intend to use these findings to inform medicines that rectify an imbalanced gut flora, thereby preventing allergies from forming.
“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,” said Dr. Turvey.
The study is part of the Canadian Healthy Infant Longitudinal Development (CHILD) Cohort Study, which enrolled families from BC Children’s Hospital, BC Women’s Hospital + Health Centre, and other pediatric facilities across Canada. Since its inception in 2008, the team of Canadian researchers has studied the health, growth, and surroundings of children from birth, making significant insights about how asthma and allergies develop.
