A new study is showing that exposure to dogs and other domestic animals is linked to a lower risk of childhood asthma, around age six.

Time reports that the study, published Monday by JAMA Pediatrics, contains research on almost 400,000 preschool and almost 300,000 school age students and found a potential positive effect from early exposure to animals.

Exposure to dogs, such as parents owning a pet dog, during a child’s first year showed a link to a 13% lower chance of asthma, in school age children. Exposure to farm animals showed a link to a 53% lower chance of asthma development in school age children, and 31% less in that of preschoolers.

The study did not directly determine the cause of the lower chance of developing asthma. Researchers do say, however, that the findings do complement that of hypotheses on hygiene. The hypothesis suggests that a lack of exposure to certain germs and microbes in early childhood could lead to a higher chance of allergies. Exposure to these things may lead to an overall stronger immune system.

Similar research has linked pets and livestock to lower allergy risk, which could have to do with the microbes in a human’s gut, which help to fight infections. Research shows that exposure to dogs is related to changed bacteria in house dust. Mice exposed to this dust have their gut bacteria altered, and have fewer overall allergic reactions.

The authors of the study say the information may help families that are unsure of when it is appropriate to introduce their children to animals.