Recent studies have suggested that exposure to cats may actually protect a child against asthma. For years scientists believed that exposure to cat allergen actually increased the risk for asthma. A study performed by the National Institutes of Health (NIH), indicates that cat exposure does indeed protect against asthma in children—with one important exception, when the child’s mother has asthma. The study was published in The Lancet [360(9335):781-82 (2002)]. If a child’s mother has asthma, a cat in the home triples the risk of developing asthma by the age of five.

The study involved 448 children who had a family history of allergies. The researchers interviewed caretakers about the subjects’ exposure to cats, as well as testing cat dander levels in the home.

Children without asthmatic mothers, who were exposed to cats, were 40% less likely to experience persistent wheezing than children who were not exposed. In children with an asthmatic mother, were more likely to have persistent wheezing. The wheezing became worse year to year. By the third year, the risk of wheezing doubled, and by the fifth year it more than tripled.