A new study from the University of British Columbia Canadian Healthy Infant Longitudinal Development (CHILD) involves more than 3,500 families and their infants across Canada who are being closely monitored to determine how genetic and a wide range of environmental factors contribute to health outcomes, especially allergies and asthma.

Researchers used data from 2,477 children and assessed the children with skin allergy testing at approximately one year of age. Tested for sensitivity to ten allergens, including cat, dog, dust mites, cockroach, fungus, milk, egg, soy and peanut. Exposure to traffic-related air pollution was assessed by estimating nitrogen dioxide levels at each child's home address.

It was published in the journal Environmental Health Perspectives and exposure to outdoor air pollution during the first year of life increases the risk of developing allergies to food, mold, pets and pests.

Subjects showed that sensitivity to allergens was associated with exposure to traffic-related air pollution during infancy. Researchers wanted to investigate increasing rates of allergies amongst children in Canada and elsewhere. Was air pollution from traffic partially responsible?The first study to find a link between air pollution and measured allergic sensitization during the first year. Infants exposed to air pollution were at greater risk. But second link found between mothers exposed to air pollution during pregnancy and allergy risk in their children.

Vancouver had the largest proportion of children to develop sensitivity to allergens. The study also found that children who live with furry pets and no attached garage were more likely to have no sensitivity to allergens.

From here we can understand  environmental exposures in early life affect the development of allergies can help parents take preventative 

Also found that children who attended daycare or with older siblings in the household were less likely to develop allergies. Exposure to other children might be a protective agent. Of the participants, 16 per cent of infants were sensitive to at least one of the tested allergens; 12.5 per cent were sensitive to a food allergen; and 5.3 per cent were sensitive to an inhalant allergen.