It's been more than a week, my neck is very itchy with no rash. i am not allergic to anything. what could possibly be wrong with my neck?

Dry skin: Itching can result from nerves, anxiety, dry skin, cold weather, and more. Drink plenty of water and apply Sarna lotion or the Gold Bond anti itch cream moisturizer. If this persists see your doctor to check you for a skin condition or discuss your possible stress that may causing this.

Many causes: You won't know whether you are allergic to something you have used (shampoo, conditioner, hair dye, sprays etc) until you look into it. If you have introduced a new hair product or lotion within the past few months, this new product would be a likely suspect. In the meanwhile, try topical hydrocortisone cream. If not helpful , see dermatologist or allergist.