I believe dogs get kennel cough from being cold-That's why dogs always get it from being at the pound- its all cement there- COLD. At home... dogs don't always do what's good for them- they sleep on cement... and the cold goes deep into their bones. They mostly sleep right at the back door so they can't miss if you happen to come out- even if it's unprotected from the rain at the door- put a mat there to save the dog from kennel cough and from arthritis later in life. I have 2 mats so that when one gets wet in the rain I move it to dry out (or to hose down wash) replacing it with the dry one.
Mine sleep in the garage on a thick dog bed and there's linoleum on the floor in the garage just so they CAN'T sleep on the cement floor (lino is cheap- and easy to mop) and they have never gotten kennel cough. Keep them warm and they may not ever get it again. I believe in Hydrogen peroxide and also in collodial silver water but not at the same time) :)