My black male rat is 1 1/2 yrs old.   He has developed lumps on his tail and chews them causing scabs. He has chewed all the black from tail base 1/2-inch down. I saw pix of ringtail--it's not that. Old age? calcium deposits? It doesn't seem to affect his happy peppy disposition.

Optional Information:
Age: 1; Male; Breed: black berkshire rat

Already Tried:
washing with chlorhexiderm soap and water. don't want to take him out in the cold. prone to respiratory infections. need answer other than taking him to a vet