We Have A Russian Blue She Is Between 3-5 Years

We have a Russian Blue she is between 3-5 years old. She has bald spots on her back, close to her
hind legs and on her belly. She seems healthy, she has a good appetite and there is no scabbing or infections where there is no hair. She is an inside/outside cat and enjoys hunting. We don't know if the bald areas are from her going thru fencing or if she has allergies. Any help is greatly appreciated.