A new study suggests that early interaction with dogs or farm animals may lead to a reduced risk of childhood asthma – a finding aligned with the hygiene hypothesis, which claims exposure to bacteria early in life can result in better immunity.
Writing in the journal Pediatrics, a team led by Dr. Tove Fall of Uppsala University, Sweden, conducted a nationwide study on the link between asthma and animal exposure, covering more than a million child subjects born from 2001 to 2010.
During the first year of life, exposure to farm animals led to a 52 percent reduced asthma risk in school-aged kids and a 31 percent reduced risk in preschool-age ones, while exposure to dogs was linked to a 13 percent reduced risk.
The study analyzed nearly 377,000 preschool-age children and 276,000 school-age ones, about five percent and 4.2 percent of which had had an asthmatic event. It obtained data from the National Patient Register as well as records of prescribed asthma medication dispensed at Swedish pharmacies.
"For what we believe to be the first time in a nationwide setting, we provide evidence of a reduced risk of childhood asthma in 6-year-old children exposed to dogs and farm animals,” wrote the study's authors, saying the information might assist in decision-making among doctors and families on when to properly expose children to animals.
The exact reason for a reduced asthma risk due to early animal exposure is not clear – it may be because of a single factor or a combination of many related to pet ownership lifestyle or dog-owning attitudes, such as children’s exposure to pet dust and household dirt, being physically active, or spending time outdoors, explained Dr. Fall.
Among the current hypotheses behind this link is that kids in animal-inhabited settings breathe air containing more bacteria and bacterial fragments, which can reduce asthma risk.
A 2001 review of previous research echoed opposite findings and showed an increased asthma risk with pet exposure. A 2012 review, however, tied dog and pet exposure to a reduced risk not only in asthma but also in allergies during childhood.
Allergist and immunologist Dr. Purvi Parikh of the nonprofit Allergy & Asthma Network said these findings are aligned with what is called the hygiene hypothesis, which promotes early bacterial exposure for shaping healthy immunity and reducing risk for asthma and allergy development.
He said that while these conditions are partially genetic, research shows that the “environment does play a key role” in nurturing the immune system.
"My take-home message from this study is that parents at this point do not need to worry about keeping their dog or getting a puppy when expecting a baby for fear of asthmatic disease," Fall advised, recommending avoiding getting a furry pet if a child is already suffering from allergies.
Photo: Donnie Ray Jones | Flickr