Hi.
Kennel cough is important to check for. If the vet says no to a physical illness or medical problem:
I would switch foods, and goto a higher quality food mixture. I have included two links of things I have suggested for others that might help for you.
http://www.yorkietalk.com/forums/sho...62&postcount=3 http://www.yorkietalk.com/forums/sho...74&postcount=8
Best,
d