How long should shampoo be kept on hair? Is it harmful to keep it on fot too long? ?

I actually read somewhere too much shampoo damages your hair, and it sounds like your scalp might be sensitive to your shampoo and conditioner, either try using less or when you go to a salon get proffesional*(not walmart brand) shampoo/conditioner, tell them that you have been using dove and its irritatting your scalp, they know what products to use and what would be best