Sadie constantly licks and bites her read legs many times a day for 5 minutes or more straight. When she licks she licks her under side around where there's no hair or on the inside of her leg until its soaking wet and sometimes til the skin turns red irritated,and the sound of her doing it and action of her doing it is driving me crazy! What could cause this? She doesn't have fleas,she does have dry skin and we only give her a bath once a month with an oatmeal shampoo. Why is she licking and biting so much?