This sounds really unlucky - hamster AND puppy kinda poorly. My hamster is a female short hair, about 8 months old. I recently went away on holiday and left her with my grandad, who kept her in a small room. When she came back 2 weeks later she was a teeny bit thinner, but my grandad looked after her well and kept one window open. But after about a week I noticed she'd lost some fur on her belly and the skin underneath looked irritated with two red spots. I cleaned her out well and thankfully it started to clear up, and the skin has improved. Just to be safe, I also applied some special powder which seems to be helping. Her fur still hasn't grown back and it's kinda thinner all over, but she has a good appetite and isn't behaving any differently. I thought it might be stress, but with my new puppy I thought she might have caught mites, although it's sorta cleared up. Today I cleaned her out again, and I noticed my brothers hamster has a small patch of fur missing near it's bum. My mum said it might be from the stress - they lived in a lively environment and they spent 2 weeks somewhere completely different - then came back again. Has anyone else experianced this before? Does it sound like mites or an allergy or stress? Please help!