Dog is pulling out her hair?

don't know...my dog ate a hole in his bum just above his tail...was a hot spot, looked scary horrible, a neighbor gave me a leave from an aloe plant and it healed over in a few days and grew hair quick..so for healing i'd recomend that....maybe theres a tic or something in the swamp thats invisible to you, something thats burrowed under her skin thats itching him . i'd take her to the vet