I've got the same 'problem', I get a sunburn easily.

I am sure there are natural alternatives, but they don't protect you against intense sun. Then again, it's never a good idea to spend too much time in the sun, with or without sunscreen. I believe moderation, as is the case with everything, is key.

Or you could try mud ;>)

P.S. Most sunscreen is full of crap and my face doesn't like it