Hi essexgirl, it`s always a good idea to have a vet check if you are worried about any symptoms. The hair loss around the hip glands can be due to various things like hormones, over scenting (the gland can darken in colour and seem `wet`) sometimes and as your vet checked for, any internal signs of a cause, although it`s nearly impossible to tell whether bodily changes are the cause or not. Mites can cause a small animal to start scratching more but seem more agitated than normal grooming, which starts and stops. Small cuts or scabs can appear usually around the nose, face, neck or shoulders. If your hamster doesn`t have any cuts or scabbing or signs of irritation apart from the hair loss around the scent glands, I wouldn`t think it`s mites. But using a spot on treatment won`t go wrong.
What you could do is look at what you use in her cage.
Wood shavings: If she`s always used these and the brand hasn`t changed, then I doubt this would be the trigger.
Hay/straw: These CAN be a cause, so stop their use if you do add these. Use plain cheap white toilet paper from the supermarket as nesting and/or any paper based stuff sold in good pet shops only.
Carefresh: This can give off a fine dust that could cause irritation, so avoid it if it`s something you have recently started to use.
Nibblets of sweet corn can be good nutrition for the skin so offer her a few of these every few days as a treat. They can be frozen or fresh but not from a tin. I take broken off nibblets that fall to the bottom of a bag of frozen corns and run them under water to thaw them.
Hamsters enjoy these.
Now, the wooden items. Freezing won`t kill parasites. Heat does. But in all honesty, I wouldn`t bother unless you knew there was some kind of parasitic infection and right now, you can`t be 100% sure.
If you do want to chuck the wooden sleeping house, the best alternative would be to get a free shoe box from a shop or any same size cardboard box and remove the floor (or the lid of the shoe box) turn it upside down so the floor is exposed beneath and just cut a few entry/exit doors in it. They are a good size, chewable and cosy. I use nothing else and my hamsters have all loved their boxes!
What age is Biscuit? What is her diet and does she get raw veggies as part of her diet? x