That's the instructions on every bottle of shampoo. Then to prevent your hair from being dry and fly-away, you "need" to apply a handful of matching conditioner. Well for years I have been washing my hair only once. And I do use just a dab of conditioner. I asked my dermatologist and she told me all shampoos are equally good. So now I buy whatever is on sale, sometimes I can even get a bottle for 79 cents. And I buy famous-name conditioner only because I enjoy the fragrance.