I have a Chihuahua that did/does this. I can give her some pills I found at Petsmart (I'm sorry but I can't remember what they are called) and she doesn't do it. I actually rarely catch her doing it anymore without the pills. It's chewable, safe, and they make it taste nasty. It will say on the box that it's specifically for that problem. Good luck!
owner of a 9 month old German Shephard, Crook, 6 year old teacup Chihuahua, Chiquis, and 5 year old Chihuahua mix, Chico