I wear a Giro wicking cycling cap under my helmet. Even without, the helmet does a good job of keeping sweat of my eyes. My old helmet, a Bell Solar, would let sweat run down and get into my eyes--the new one, Specialized Echelon, does not. I use the cycling cap mainly for the bill so I can keep low sun out of my eyes, but I have found that the cap keeps my hair drier as well. I'm also lucky. It takes a lot of heat and humidity before I sweat a lot. I never been much of a sweater. So if I'm covered in sweat, it's bad out there.