I have only started using one in the last 6 months or so. Although I don't think a primer is essential it glides onto the skin and does seem to provide a smoother base for make up and gives it more staying power. As citygirl said, Smashbox have one called Photofinish, which goes on clear with a silky texture and you only need the tiniest amount. (You can buy Smashbox from QVC, by the way).