Uni hates it. She won't give us any kisses after brushing our teeth or Listerine-ing, putting on Burt's Bees lip balm with mint (but will with Burt's Bees without mint), won't take bites of fresh mint, but will take almost any other herb. I think there is a bit of "vapor" that comes off of mint, either fresh or in a product. Maybe it burns her mucous membranes?
Does your yorkie like mint or abhor it? She didn't like mint breath tabs or mint toothpaste either. It's CET chicken flavor all the way.