Researchers discovered that children were more at risk of developing asthma if there was a dog in the home. This risk increased if there was a canine companion around, but not a cat.
According to the journal Pediatric Allergy and Immunology, 380 children at high risk of having asthma because of family history participated in a study. The researchers found that children exposed to the presence of dogs before the age of seven were more likely to develop the disease.
This was not the case with cats and nobody knows exactly why. One theory put forward focuses on endotoxin, a substance produced by bacteria that is known to trigger inflammation in the airways.
Lead researcher Dr. Chris Carlsten works at the General Hospital in Vancouver, British Columbia, He says, "Dogs tend to have a lot of endotoxin on them, because they’re dogs. In contrast, cats have much less."
According to him, more research needs to be done. He adds, "This study doesn’t answer it. And in general, there is not enough evidence to recommend for or against pets."