A B.C. researcher has found a long list of early childhood allergies may have a common cause — and possible solution — living in their gut.
The study, published in the journal Nature Communications this week, analyzed the microbiome of bacteria in children’s gastrointestinal tract, and how they influence the development of allergies in the first five years of their lives.
“By identifying infants with this interesting bacterial signature, we may be able to provide early support to prevent these allergies later on in life, and actionable things that could be done,” said Courtney Hoskinson, the lead author on the study and a PhD candidate at the University of British Columbia’s Department of Microbiology and Immunology.
From birth, Hoskinson and 12 other researchers tracked more than 1,100 children drawn from across Vancouver, Edmonton, Winnipeg and Toronto. By age five, more than half the participants had developed at least one of the four allergic disorders, including eczema, asthma, hay fever and all sorts of food allergies.
To assess how those allergies were connected to gut bacteria, the researchers then examined stool samples collected during doctor checkups at three months and one year old.
The results showed the emergence of the allergic reactions were all connected to gastrointestinal systems that had been thrown off balance.
While children who had the right equilibrium of microorganisms in their guts tolerated the allergens, those who developed an allergic disorder all showed signs the bacterial biomes of their digestive systems had been disturbed.
Infant exposures vital to avoiding allergies
The disturbances in gut equilibrium were most obvious at birth, according to Hoskinson, who also works as a researcher at BC Children’s Hospital.
“Right when we’re born, we begin to be colonized by the bacteria we’re exposed to,” she said.
Children who undergo a caesarean birth into a sterile hospital environment aren’t exposed to the beneficial microbes in the mother’s vaginal canal. Those who aren’t breast fed don’t get the key sugars which feed the ‘good bugs’ so they can outcompete the bad ones and fill an ecological niche in an infant’s digestive tract.
Hoskinson said a lot of the bacteria that we consider to be beneficial in protecting against allergy can produce metabolites that strengthen our gut barrier and prevent uncontrolled interactions between different foods and our immune system.
“They're kind of mediating that relationship,” she said.
Without those bacteria, our immune systems can become “abnormally educated” and attack typically harmless foods or other environmental exposures, essentially triggering an allergic reaction.
“We shouldn't consider them dangerous,” said Hoskinson of some allergy producing foods. “But if our immune system becomes confused, then we can develop that allergy.”
Past studies have linked specific bacteria within the infant gut to individual diagnoses, such as asthma and food allergies. Hoskinson worked alongside a dozen colleagues spanning eight major Canadian hospitals and institutions: UBC, BC Children’s Hospital, University of Manitoba, University of Alberta, University of Toronto, McMaster University, The Hospital for Sick Children in Toronto and the Children’s Hospital Research Institute of Manitoba.
Together, the research team identified a common bacterial signature that may be universal to the development of major childhood allergies.
“We do find a group of them that are really important to the community as a whole,” Hoskinson said.
What matters, she added, is maintaining that microbial balance throughout early childhood.
Environmental exposures help build immune system response
After a child is weaned, a long list of other environmental exposures have been shown to either help or harm the development of a child’s gut bacteria, says Hoskinson.
That begins with food.
“Once you switch from breastfeeding to that more solid table food diet, the exposure to different types of foods that you have can definitely influence whether or not you're allergic to them later on,” she said.
That logic has recently been turned on its head. Where once pediatricians recommended parents avoid giving children common allergens, today that advice has been reversed.
“There has been a major shift in recent years,” said Hoskinson. “If kids don't already have a predisposition to being allergic to these foods, the earlier that they are exposed to them and can eat them and can develop a tolerance to them, the safer they are to developing an allergy to them.”
In other words, exposing young children to a variety of food early on can help establish normal immune responses, even to things like peanuts.
Let your kids play in nature, say experts
Another important environmental exposure that could help ward off allergies: playing in the dirt.
Past research has found being outside in nature boosts mental and physical health at all ages. The benefits are so obvious to many scientists that doctors in Canada recently came together to prescribe time in nature, including prescribing passes to national parks and most recently the Canadian Museum of Nature in Ottawa.
Hoskinson says letting infants play outside in the dirt of a field or forest where they can be exposed to a diverse community of beneficial bacteria will help them stimulate their immune system and “create the correct recipe within their gut.”
At the same time, Hoskinson acknowledged there’s an important balance to strike. Things like hand washing and hygiene are really important for reducing infections, and prevent the spread of a very different type of bacterial environment than what’s found in nature.
“Household cleanliness, you know, it's very important,” she said. “But having kids get outside or getting exposed to environmental microbes that can be in dirt and trees, that can be good for their gut bacteria to properly develop as they get older.”
After breastfeeding, children who eat a diverse, nutrient-rich diet will also help feed themselves and the bacteria that live inside them.
Hoskinson offered a final warning: reduce unnecessary exposures to antibiotics, which can kill harmful pathogens but also tend to wipe out the beneficial bacteria that could protect us from allergies.
“We really only want one use for antibiotics — when they're absolutely needed,” she said.
