We have an 8 year old staffie cross who has started to go bald on his flanks. He has already been neutered and is on a gluten free diet. However for the last couple of months we haven't had much sun and he spends a lot of time in his kennel, which is dark. I was wondering if it could be that causing the problem but I've also read that it could be a thyroid problem. Do you have any suggestions?

It could be bald spots from laying on a hard surface, is there bedding in there for him? Does he have fleas? Is he chewing his paws? It could be something other than gluten that is causing him to itch and scratch.

He's got plenty of bedding, not got fleas, not chewing or scratching and generally seems really happy. It just doesn't look very nice

There are a few medical conditions that may cause this, Cushings might be one. If you decide to take her into the vet they will do a skin scraping and look under a microscope to determine if it is a skin condtion (mange etc... ) If the fur continues to fall out they might investigate further with more tests etc... It could also be ringworms, this also causes hair loss. Is there any odor or crusty-ness?

Can you post a picture of it?

He may be mixed with boxer... Boxers have a genetic disease where they go bald on the flanks and sides. It's called boxer alopecia. I think melatonin once a day is what helps bring hair back. You could try it. Melatonin is a natural medicine you can purchase at Walmart. Talk to your vet about boxer alopecia