Is there a home treatment of natural antibiotics for dogs for kennel cough?

I just got a puppy from the pound and he had kennel cough, I took him back and they said that there is no treatment for this. They did give him antibiotics for a possible secondary infection but kennel cough has to run its course much like a humas virus has to. They did say I can use Robitussin DM for the coughing symptoms. The puppy is fine but now my older dog has it, the vet said we have to let it run its course but she looks so miserable. I am giving her robitussin but I want to give her a boost of natural antibiotics that are safve for dogs. I did get some drops from the health food store but they do not have any antibiotic properties.

HELP! Thanks

With the rubitussin it should only last a few days. I do use lysol spray all around the house. They will sneeze when you first spray it.