Could I be allergic to my shampoo as my head has gotten abnormally itchy and dry since a shampoo change. More dry than normal winter skin.?

ALLERGY SHAMPOO. It sounds as if you might, indeed, be allergic to a shampoo or to any other hair cosmetic you may be using such as a conditioner, spray, rinse, etc. Use a bland shampoo, such as johnson's baby shampoo for a week or more, and see if this alleviates the problem. If not, check in with a dermatologist.