A peeling scalp from a previous sunburn is gross, and I've had my share of skin cancers. My fault as I LOVE to run on nice bright sunny days, and I can't find a sunscreen that doesn't give me a rash :-( I usually wear a white mesh cap on hot sunny days. The BEST is when you can grab a handful of ice and stick it under your cap as you run. Feels SO good.
Marathons don't usually have ice tho :-(