Kids who grow up with a dog in the house may be at higher risk of developing asthma if they’re also exposed to secondhand smoke or nitrogen dioxide, new research shows.

Children exposed to the toxic gas and to dog allergen during their first year of life were nearly five times as likely to have asthma at age 7 compared to kids with neither exposure, while dog allergen plus secondhand smoke nearly tripled the risk.

Most studies of asthma in children have looked at single risk factors, but in the real world, people often face multiple exposures, Dr. Chris Carlsten of Vancouver General Hospital in British Columbia, Canada and colleagues point out in the European Respiratory Journal.


To investigate the interplay between such exposures, the researchers looked at 380 children at high risk for asthma who had been followed since infancy.

While the exact mechanism through which these exposures could increase asthma risk isn’t known, gas and particles could damage the lining of the airways and trigger inflammation, the researchers say.

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