Infants living in households with dogs were healthier and had fewer ear infections than those without a dog, the study found. Researchers also found that cats appeared to offer some protection, but the link wasn't as strong.

The study, posted online Monday and based on 397 children who lived in rural and suburban parts of Finland, examined whether contact with dogs and cats during a baby's first year offers any protection from respiratory tract infections, such as colds and resulting common ear infections. 'The children having dogs at home were healthier, they had less ear infections and they needed less antibiotics,' said Eija Bergroth, the study's lead author and a pediatrician affiliated with Kuopio University Hospital in Kuopio, Finland.

One measure showed children with dogs were reported as being healthy for about 73% of the time, based on weekly questionnaires, compared with about 65% of children with no dog contact at home. While the study tracked just under 400 babies, the researchers said the results were statistically significant because it relied on weekly questionnaires filled out by parents.

Dr. Bergroth explained that children who lived in households where dogs spent 18 or more hours a day outside, showed the most healthy days, fewer fevers and the least use of antibiotics compared with babies with no dog at home. One theory is dogs that spend a lot of time outside likely bring more dirt and bacteria inside the home compared with dogs and cats that spend more time indoors, she said. Researchers believe that exposure to dirt and bacteria builds up babies' immune systems.

Researchers found that 97% of babies-whose mothers were enrolled in the study during pregnancy-had a runny nose at some point during the study, most had a cough and about 40% had an ear infection. Nearly half of the children needed antibiotics.

Earlier studies using smaller samples of children have shown conflicting results on the impact of animal exposure on infections and allergies, though a study funded by the National Institutes of Health showed children exposed to two or more dogs or cats in their first year had lower chances of later developing all kinds of allergies than children exposed to one or no pets.

Dr. Bergroth's study involved children who were born at Kuopio University Hospital in Finland between September 2002 and May 2005. The children's parents were given weekly questionnaires from the time their babies were nine weeks old until they were 1 year old. The questionnaires asked if the children had been 'hale and hearty' in the past seven days. If the child wasn't healthy parents were asked to document ailments like fever, cough, runny nose, ear infection, diarrhea, urinary tract infection or rash. Families were also asked each week if they had a dog or a cat at home and how much time the animals spent outside.

The study results were tabulated looking at responses on the weekly questionnaires rather than individual children. Researchers analyzed the data in different ways to rule out other factors that could influence infection rates like breastfeeding, low-birth weight, the number of siblings and whether moms smoked during pregnancy.