Back in the fall, Oscar developed a hot spot on his side. We took him to the vet, who gave him a shot and gave us some medicine to use to treat it. That hot spot was kind of an oozing sore--very nasty looking. Now he has a round bald spot on his head behind his left ear. Could this be another hot spot? It doesn't look like the first one did. It could be some other kind of allergic reaction.