Clover had an abcess a while back, her and one of Mel's kitties must have been playing too hard, and she got a lump on the top of her head, and she'd even balded (the fur kept growing under the skin) there for a while. We took her to the vet and the first thing he said was, "She's got a pimple..."
I could NOT watch as they got the hair and gunk out of it.
She got an antibiotic cream, and now she's doing just fine. SHe even has hair! XP