Itchy pin needle feeling all over back. what could it be?

Pins and needles: Itch, pins and needles sensations all over your back but not on other parts of your body may be a reaction to heat or to material that comes in contact with the skin of your back. If you have abnormally dry skin, rub in a moisturizer like alphakeri or eucerin while your skin is still wet after showering. Widespread parasthesiae can be due to deficiencies of calcium, magnesium or potassium.