A dog that purrs and seems to have phlegm but does not cough may be caused by an upper respiratory tract infection. It is best to go to the hospital for examination and timely treatment to avoid delaying the condition or aggravating the condition. Generally, upper respiratory tract infections are caused by bacterial infection, viral infection, allergies or parasites. During the breeding process, regular disinfection is required. Do not take your dog to play in dirty places, and do not let your dog smell irritating food. The smell, deworm the dog regularly.