Hi, it looks like either an allergy, maybe to food?, or I think it could be an irritation. What type of food bowls do you use? The best bowls to use are stainless steel bowls, and they should be rinsed out after every meal and dried, and washed at least once a day. I always wipe the bowls out in the morning and then wipe it dry with a paper towel, and then after their dinner in the evening I place the bowls in the dishwasher. If you use plastic bowls, they can get cuts or scratches in them that can hold on to bacteria and cause irritations on the chin. It always a good idea as well to wipe and dry the chin and mouth area after eating. A wet or damp chin can also cause irritation and rashes. Another cause of irritation can be tap water, have you tried switching to filtered water? We use a pet water dispenser with a built in filter, or you can use a Brita water filter or other type. I hope it clears up soon. Keep the area clean and dry, and you can try some Polysporin as well.