The most common cause of severe pruritus, or itching, around the tail, is a flea allergy.
It doesn't have to be alot, just one bite and it starts a vicious cycle of chewing around the tail and hind legs.
Your dog would benefit from a once a month flea prevention like Advantage, some antihistamines like benadryl (25mg every 12hrs as needed) and if the chewing is significant, a short acting steroid from your vet to stop the cycle.
Living in SC the freezing doesn't come long enough to get a true kill of fleas, and they do live in the house...so a flea prevention is key to prevent it from constantly happening.
Good Luck,
Dr.V
Dr. D.A. Vamvakias
Veterinarian