Just took Bella to the Vet last week w/this problem (and feet licking). Vet asked if I used PLASTIC BOWLS for food/water. I said yes - she said STOP. The chin "bumps" are a reaction to the chemicals in the plastic. She said use stainless steel bowls. Bella has been using the same 3 plastic bowls for 4 years & I rotate them through the dishwasher. Of all the things I "thought" might be the cause of her "chin bumbs" - the bowls would have been at the bottom of the list.