My cat is grooming herself her hairless!!!

My 7 y.o. female tabby (Katrina rescue) is an incessant groomer -- so much that she has no hair on her lower belly and inner rear legs. She's spends a lot of time licking, chewing and grooming. She's completely an indoor cat with no visible signs of bugs or dry, flaking skin. She otherwise seems healthy and well-fed.

Any ideas?

Take her to the vet to rule out any allergies or other issues. If she's got a clean bill of health then it could be behavioral/emotional.