Have her skin-scraped ASAP since it could be Scabies or Demodex mange mites. Other causes for hair loss are fleas, or flea allergy dermatitis, food or environmental allergies, endocrine disorders such as hypothyroid, auto-immune disorders and more, best sorted out by your vet.
I have a similar problem w/my 10 yr old Roti mix. I posted "at my wits end" about her condition. She has been skin-scraped. It's not mange or scabies. I think I will have her thyroid checked but it's so expencive. I'm in debt over this problem as it is.
Thank you for being here Dr Cheng.
Thank you so much for the compliment!
A thyroid profile is not too costly, but at her age you should really have a full senior profile including a urinalysis. My Clinic charges $140.00 for a senior profile including a T4 (screening test for hypothyroid), and urinalysis. I would also have her checked for Cushings Syndrome if she is losing fur without being itchy. I have mentioned before about Care Credit which is an interest-free credit card for medical and veterinary bills. It is worth examining.
If she is itchy you could try a limited ingredient, novel protein diet such as venison and potato, or sweet potato, and just feed her this and filtered water for 8-12 weeks. There can be no cheating! Food allergy dermatitis can occur at any time in a dog's live.