Personally, I try to never skip a toner in my daily skin care regime. I love the way my skin feels after a toner, and I really can see the difference on the cotton pad after I apply it. But is it necessary? Probably not. I stand on the side that says yes, you should use a toner to encourage healthy skin.
There are many professionals who disagree with me however; stating it really is an unnecessary step in your skin care regime unless you have oily skin or just love using a toner.