Exposure to dogs reduces risk of asthma in children

Contrary to common parental fears, early exposure to dogs and farm animals can reduce children's risk of developing asthma, says a new study. The research borrowed on earlier findings on impacts of growing up on a farm.

The Swedish researchers studied data covering more than a million children born between 2001 and 2010 in Sweden. During this period, registering pets were made compulsory.

They found a 15% decreased risk of asthma in six-year-olds following exposure to dogs in the first year of life. Farm animal exposure cut the risk by 52%. The findings were true even in cases where the parents had asthma.

Earlier studies on farming and asthma have found children with early exposure to farm animals had a 25% lower risk for developing asthma, compared with those who did not grow up on a farm. The present study further supports the hygiene hypothesis that suggests sterile conditions increase a child's susceptibility to allergies. "If we look at this history, we've been living with dogs for a very long time," says Tove Fall, an assistant professor of epidemiology at Uppsala University in Sweden and a coordinator on the study. "It's the first pets we had."

How exactly the presence of animals boosts immunity is not understood though the scientists suspect it could be due to the effect on the child's microbiome (bacteria environment in the gut) or simply that children with pets exercise more and spend time outdoors. Fall's team hopes to find more about the link.

However, children with established allergy to cats or dogs should avoid them, said the researchers. The findings of the study were published on Monday (2 November) in JAMA Pediatrics.

The researchers were all praise for Sweden's organised system of national databases that scientists can access. Right from birth, details about a child's visits to the doctor are recorded and kept in a single database.