Major childhood allergies - eczema, asthma, food allergy and hay fever -- may likely begin in the community of bacteria living in our gut, according to a new study.
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.
"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 Paediatrics at the University of British Columbia.
"Hundreds of millions of children worldwide suffer from allergies, and it's important to understand why this is happening and how it can be prevented," added Turvey, an investigator at BC Children's Hospital Research Institute.
The research, published in the journal Nature Communications, examined how these types of influences affected the balance of gut microbiota and the development of these allergies that affect more than a third of people worldwide.
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 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," said Courtney Hoskinson, a doctoral candidate at UBC.
"We found a common breakdown in these mechanisms in babies before the development of allergies," she added.
The findings could lead to methods of predicting whether a child will develop allergies and ways to prevent them from developing at all.
"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," Turvey said.
