Childhood allergies can be caused by a variety of factors, but one common component that contributes to many significant childhood allergies is an overactive immune system that misidentifies harmless chemicals as dangerous.
According to a new study led by experts at the University of British Columbia and BC Children’s Hospital, several main childhood allergies may all be caused by the community of bacteria living in our gut.
The study, which was published in Nature Communications, finds gut microbiome traits and early life variables that are linked to children having any of four major allergies: eczema, asthma, food allergies, and/or hay fever. The discoveries could lead to methods for predicting whether or not a kid will acquire allergies, as well as methods for preventing allergies from occurring at all.
“We’re seeing more and more children and families seeking help at the emergency department due to allergies,” said Dr. Stuart Turvey, a UBC professor of pediatrics 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.”
Normally, our bodies tolerate the millions of bacteria that live in our guts because they do so many good things for us. We tolerate them by maintaining a strong barrier between them and our immune cells and by limiting inflammatory signals that would call those immune cells into action.
Courtney Hoskinson
The study is one of the first to look at four different school-aged pediatric allergies at the same time. While each of these allergy disorders has its own set of symptoms, the Turvey lab wondered if they could be linked to the composition of the infant gut flora.
“Because these are technically different diagnoses, each with their own set of symptoms,” says Dr. Charisse Petersen, co-senior author of the article and postdoctoral scholar in the Turvey group. “However, when you look at what’s wrong at the cellular level, they actually share a lot.”
For the study, researchers examined clinical assessments from 1,115 children who were tracked from birth to age five. 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 bacterial signature seen in the stool samples was linked to the children getting any of the four allergies by the age of five. The bacterial signature is a symptom of dysbiosis, or an imbalance in the gut microbiota, which has likely resulted in a weakened intestinal lining and an enhanced inflammatory response within the gut.
“Normally, our bodies tolerate the millions of bacteria that live in our guts because they do so many good things for us. We tolerate them by maintaining 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 the paper’s first author. “We found a common breakdown in these mechanisms in babies prior to the development of allergies.”
Diet, how we are born, where we live, and our antibiotic exposure are all factors that can influence the baby’s gut flora. Antibiotics, for example, may wipe out sensitive bacteria, but breastfeeding tends to restore and supply required food for bacteria in the infant’s gut. The researchers investigated how these types of factors altered the balance of gut bacteria and the development of allergies.
“There are a lot of potential insights from this robust analysis,” adds Dr. Turvey. “Based on these findings, we can conclude that factors such as antibiotic use in the first year of life are more likely to result in later allergic disorders, whereas breastfeeding for the first six months is protective.” This was true for all of the allergy diseases we investigated.”
Now the 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,” says Dr. Turvey.
