Hi
Welcome to the MedHelp forum!
Dry skin is the commonest cause of itching. Applying a moisturizer and using only soaps that are gentle on the skin is helpful in this case (as you also find). Hypothyroidism too causes dry skin. Please get your thyroid function checked. It could also be due to overuse of AC and heaters. If you have blisters and dry skin then you need to rule out certain conditions such as diabetes, psoriasis, hypothyroidism, contact dermatitis, atopic dermatitis and malnutrition.
Since I cannot examine you and know other related conditions you may be having, nor is a detailed history possible on net, I have listed the various possibilities that should be looked into. Please consult your PCP for primary examination followed by proper referral. Take care!
Try Aveeno lotion. Flaxseed oil capsules helped me greatly and swiftly.
I too would run very very hot water and the relief was soooo soothing. Good luck.