Bacteria in the gut are linked to childhood eczema, asthma, hay fever and allergies to certain foods, suggests a Canadian study, and researchers note infants who are prescribed antibiotics are at greater risk of developing one or more of theconditions.
Dr. Stuart Turvey, one of the senior researchers of the study published Tuesday in the journal Nature Communications,said disruptions to a maturing microbiome have the immune system waging a battle against innocuous foods or pollens including grass, in that case triggering reactions such as a stuffy nose, sneezing, coughing and swollen skin under the eyes.
The risk of developing at least one of the major allergies more than doubled by age five for kids who had been prescribed antibiotics before their first birthday because the medication wipes out protective bacteria and introduces harmful ones that cause burdensome lifelong impacts, Turvey noted.
"We linked that back to the structure of the microbiome because what we know and understand, through this work and other work, is that the early-life bacterial colonization is key for training the immune system and helping it to know what it should react to and what it shouldn't," said Turvey, a pediatrician and investigator at the BC Children's Hospital Research Institute.
"The immune system becomes confused and that lies at the heart of these allergic diseases," said Turvey, also a professor at the University of British Columbia who led the study that involved multiple universities across the country.
The study considered eczema, asthma, hay fever and food allergies together, though their unique symptoms mean they have typically been researched separately.It included 1,115 children who were tracked from birth to age five, with 523 of them having no evidence of allergies. The remaining 592 kids had been diagnosed with one or more allergies by age five. Of the latter group, 367 of the children had eczema, or atopic dermatitis, 165 had asthma and some suffered from three or all of the conditions.
Researchers evaluated each child's microbiome from stool samples collected at clinical visits when they were three months and a year old. The samples showed a "bacterial signature" associated with the children developing any of the four allergies by age five. The signature is considered a hallmark of dysbiosis, or an imbalance between good and bad bacteria in the gut, making people prone to allergies.
The data that researchers used was from the Canadian Healthy Infant Longitudinal Development (CHILD) Cohort Study, the largest population-based study in the country since its launch in 2008.
Turvey said a powerful message of the study is that antibiotics should not be used unless the medication is absolutely necessary for a bacterial infection. That can include an ear or a bloodstream infection or something as severe as meningitis. Antibiotics do not work for viral infections.
"But we know that many antibiotic prescriptions in that first year of life are not for bacterial infections and could be avoided," said Turvey, adding parents should also be educated about the drugs' role in disrupting the microbiome.
"Some parents will come to the clinic, essentially demanding antibiotics," he said.
The study also bolstered previous research that found breastfeeding babies up to six months is a protective measure because the milk has bacteria that promote a healthy microbiome.
Turvey and his colleagues hope their work will lead to treatments or ways to predict whether a child will develop allergies, which affect one in three kids in Canada and millions around the world.
"They're the No. 1 reason children come to the emergency room, the No. 1 reason children miss school, the No. 1 reason for billing our health-care system in Canada."
Jennifer Gerdts, executive director of the non-profit Food Allergy Canada, said milk and eggs are the most common culprits but some people interpret an allergy to milk as lactose intolerance although each condition has very different consequences.
Food allergies can create a lot of anxiety for parents who worry about their children being exposed to unsafe food in different settings, especially when they rely on others to understand the condition, she said.
"It comes with a serious psychological impact because there's that fear of not being able to control the environment that you're in, that fear of the next reaction."
About 40 to 50 per cent of children with food allergy also have asthma, Gerdts said.
"They are all tied together. I think that's what's interesting about this (study), that there may be possibilities for the research community taking a look at this and saying 'How can we explore the treatment possibilities for those that have the highest burden of allergic disease across all of these?'"
Her twin sons, now 21, were both diagnosed at age three as being allergic to peanuts, eggs, sesame, seafood and fish. They also had eczema.
They were diagnosed after they had an anaphylactic reaction to seafood and ended up in an emergency room, Gerdts said. She happened to have an EpiPen in a first aid kit the family took on camping trips.
The device is used to quickly deliver a measured dose of epinephrine, which reverses the symptoms of anaphylaxis and potentially saves someone's life.
Gerdts said education is crucial for the public health concern but childhood allergies remain under-recognized because most of the kids look healthy — until they have a severe reaction.
In the new school year, Food Allergy Canada will be offering a national food safety program that has already been launched online. It was piloted at 55 schools in Ontario, New Brunswick and Alberta in May with "outstanding results" showing 97 per of them would teach it again, she said.
"All About Food Allergy" for Grade 4-6 students is meant for children with allergies as well as those who could be a "food allergy ally," she said.
"If you can cement the understanding in kids that this is a serious medical condition with the science behind it, that this is what's happening in a child's body, then it becomes just a part of life."
This report by The Canadian Press was first published Aug. 30, 2023.
Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.
Camille Bains, The Canadian Press
