"recent research at the University of California indicates that sunscreen needs to be reapplied within 2 hours in order to remain effective. Not reapplying could even cause more cell damage than not using sunscreen at all, due to the release of extra free radicals from absorbed chemicals." (Wikipedia) OMG, this really has me worried! I have only recently started using sunscreen on my face every day, but I only apply it in the morning and then midday, if I am outside a lot. But this sounds like we have to apply it every 2 hours to prevent cell damage. And what about when the sun has set? Do we need to clean our face immediately in order to prevent damage form the absorbed chemicals? What do you think?