Hi guys, one of my hamsters' fur seems to be thinning behind its ears and neck. I've checked it -- its skin is perfect, no scabs, no mites or anything, and after sandbathing the fur looks a lot better but the next day it clumps up and looks bald again.

I suspect it is due to a mix of oily fur + it likes sleeping upside down on the wheel, and I think it likes to pee in the wheel as well. My hamster hates sandbathing, I have force it upon her, but there's still a bald patch.

Otherwise, my hamster is as active as ever and as greedy as ever, no change in attitude, activity or appetite.

Anyone encountered this problem before?