" led by Dr. Susan Lynch from the University of California in San Francisco. This study collected dust samples from homes with and without dogs, and showed that upon exposing mice to the different dust samples, the mice that were given dust from homes with dogs were less likely to develop asthma. What’s more, they looked at the type of bacteria in the dust samples and found a specific species, Lactobacillus johnsonii, associated with the improvement of asthma in mice. When they grew this bacterium in the lab and fed it to mice in the absence of any dust, they found that it lowered the risk of asthma, demonstrating that this and perhaps other species of beneficial bacteria, along with the dogs that bring them into households, are responsible for decreasing asthma risks. "

― , Let Them Eat Dirt: Saving Our Children from an Oversanitized World