Q. My chihuahua has black looking spots on him looks like dirt and sometimes it like he cannot open his mouth.
DR. CHRISTIE LONG, D.V.M., C.V.A.
A. While spots of black pigmentation on the skin can be normal, if you are noticing many of these skin changes recently I would recommend getting them checked out. As for not being able to open his mouth, this is very concerning, and could be the result of a neurologic problem or an immune disease known as masticatory muscle myositis. I would get this checked out right away to see if your vet can determine what's going on.