I have a Chihuahua who is not quite 2 years old. Yesterday, without injury, he formed this rough pebble like scab in the corner of his mouth. It doesn't appear to hurt him, because he does let me look at it, but I am worried about him. Of course I am calling the vet first thing tomorrow. Has anyone ever seen these before? All of a sudden he has been itching and scratching, so I was wondering if this was all allergy related. He went outside this evening and came back in the house.....the black scab was gone and there is a pink raised weird bump now.