How can I stop my dog from chewing on herself?

I have a 9 year old bichon frise. She does have allergies around a certain time of year. She chews on herself whenever I'm not looking. We used to get a hydro cortisone shot, but since she has been diagnosed with diabetes the vet said she can't take it anymore. He gave us pills, but they won't work. We tried sprays too. She chews herself raw and it looks pretty painful. Is there an easier way to make her stop?