Pet rat has a lot of scabs all of a sudden?

My rat Sadie, has been scratching a lot lately.. I decided to give her a bath today, she usually gets a bath once a month, since she hates it so much. While bathing, I noticed a rash of scabs from her front leg shoulder all the way up to her chin. They are small and fresh. She doesn't have mites or fleas or anything... I keep her cage clean, she sleeps in a cloth hammock with soft baby blankets and I use the soft recycled paper bedding... so there isn't anything in her cage that could be itchy.. I don't know why she is digging so much and making herself bleed. Any suggestions?