Some parents worry about keeping a pooch in the house when they bring home a new bundle of joy, concerned that the pet could be harmful to the infant's health, or that a jealous dog could become aggressive. But according to a new study published this week in the journal Pediatrics, dogs actually make babies healthier. The report presents strong evidence that babies living in households with dogs, and to a lesser degree, cats, are actually better off than kids living in pet-free homes. Here's what you should know: 

How did researchers conduct this study?
The authors tracked the health of 400 babies, and sent the families weekly questionnaires from the time the kids were 9 weeks old until they turned 1. Parents documented things like runny noses, coughs, and ear infections, and also kept records of any medications their children were given. Controls were applied for other factors that could potentially increase a child's infection risk, including attending daycare, having asthma, or having parents who smoked.

What did researchers find?
A child under the age of 1 who regularly plays with an outdoor dog — that is, a pup who spends just six hours of its time inside each day — will build a stronger, healthier immune system in the long run. Kids living in homes with such dogs were illness-free 73 percent of the time, whereas children living in homes without pets were healthy only about 65 percent of the time. Overall, dog-friendly babies "had fewer ear infections, and they needed less antibiotics," says lead author Eija Bergroth.

Why is having a dog advantageous?
Researchers have at least one explanation for the "puzzling pattern," says Amina Khan at the Los Angeles Times: "Pets that spent more time outdoors brought more dirt into their homes, giving babies more opportunities to encounter it." The thinking goes that this strengthens a child's immune system and causes natural defenses to mature faster than they normally would. 

What about cats?
Cats appear to offer similar protections, says Jennifer Corbett Dooren at The Wall Street Journal, "but the link wasn't as strong." Why? Perhaps because dogs tend to amass more dirt and bacteria than their slightly more hygienic feline pals.

Does this mean all parents should get pets?
Not necessarily. The one problem with this study is that researchers looked at the link between health and pet ownership only for extremely young children; slightly older kids may not reap the same benefits from having Fido around, says Them Pechefsky at Mommyish

Sources: Los Angeles Times, Mommyish, Wall Street Journal