It's generally recommended to use dry scalp shampoos as needed, rather than every day. Over-shampooing can strip the scalp of its natural oils, which can make the dry scalp worse. If your scalp is particularly dry or itchy, you may want to use a dry scalp shampoo 2-3 times a week, and gradually decrease frequency as your scalp improves. Always follow the instructions on the product label and consult with a dermatologist or healthcare professional if you have any concerns.