Feline asthma is a common and serious respiratory disease. Although most cats breathe in pollens, dander, mites and molds with no problem, some cats have a serious immune reaction leading to airway inflammation (i.e., asthma). Until recently, the lung was considered a sterile organ. Cutting edge technology to identify bacteria using sophisticated laboratory tests in place of routine cultures has now identified a multitude of bacterial species in the lung. These communities of “beneficial” bacteria called the airway microbiota help maintain the health of the lung. When the populations of bacteria shift as can occur with inflammation, “bad” bacteria may contribute to perpetuating inflammation in asthma. Our research has shown clear differences in the bacterial populations in the lungs of healthy versus asthmatic cats. We have also demonstrated administration of oral probiotics will change the airway bacterial communities in healthy cats. In this grant, we propose to investigate differences in bacterial populations between asthmatic feline airways in cats given standard therapy (steroids) either with probiotics or with placebo. We will also investigate how probiotics may affect control of asthma and immune responses. Results of this study may pave the way for using probiotics for pet cats with asthma by manipulating the airway microbiota to shift towards growth of “health-promoting” bacteria that diminish allergic inflammation.