I never used to have a problem with helmet hair, but now that I am sporting an afro, it's a whole different ballgame. Jamming my hair under the helmet results in several rows mini-mohawks by the time I reach my destination, and even light sweatiness generated by riding means that it takes even longer for the hair product that I use to dry, which means that I'll have a sort of whitish sheen on my hair until it does. Unacceptable on both counts. I solve the problem by only wearing my helmet on my way home for the day. That's not a solution for everyone, but it works for me.