Bald patches of fur with lumps?

Question
Are you absolutely positive this could be it?

She has been scratching constantly for the past day, and I'm now thinking if she could be allergic to the Cotton Wool bedding, as I read up on it that Russian Dwarf Hamster's can be very sensitive to bedding and sawdust used for its cage.

I will change everything tommorrow, and try Mite spray and such, and see if the problem continues to occur.

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Followup To

Question -
I recently changed my Hamsters cage, and in doing so I noticed that she has two small patches of missing fur, with what look like small bumps underneath the skin.

Because I had no original bedding left, I used toilet paper.

Could this be what is causing the patches? Or may it be something else?

http://img226.imageshack.us/img226/6646/hamster1gt6.png

There is an image of the problem, she seems to be scratching quite a lot but there is no dryness or other skin problem other than the patch.

The bumps feel like her bone.

Answer -
You're the first person to send me a picture of your animal. This really helps a lot. *looks at picture* Wow those are big bumps!! Okay what I really think they are is tumors. To find out if they are cancerous or not the vet would have to run tests. If they are cancerous tumors there may be a few options. One is to let your hamster live with the growths, one may be to have surgery and have them removed, but I don't know a lot of vets that actually perform the surgery because they are so small, and the other one which everyone should be prepared for is to have your hammy put to sleep. I do believe the surgery on such a small animal can be very expensive. I doubt if the tissue paper caused the lumps to form because tissue is generally better than wood shavings in my opinion. I would really take your hamster to a vet though. That's really the only option to do if you want to find out the what the bumps really are and what's the best way to treat them. Good Luck and keep me posted.

Answer
If you honestly think it's the bedding then I would take out any bedding and see if the bumps go down. It is true that hamsters are sensitive to certain types of bedding especially woodshavings and beddings with scents, now if your toilet paper had scents on it than yes it could cause many serious problems. If it was plain tissue with no added scents or lotions than it shouldn't affect your hamster like this in my opinion. Carefresh bedding is what I use for my hamsters bedding but it's basically tissue. Generally most vets will tell you to try kay kob bedding to rule out allergies and also prescribe medication. But I really don't think it's mites because mites cause more than just scratching. They also cause skin problems such as scaley red skin. If the bumps don't go down than look at another option such as growths or tumors.