I went to the dermatologist because I was getting dark patches on my face. Although it was caused by hormones, sun exposure made the problem worse. My dermatologist recommended this sunblock. It is a physical sun barrier, not a chemical one. It is also tinted, so it helps to cover any irregularities in your skin tone. I absolutely love this stuff. It is a little pricey and only available at your Dr's office, but it is totally worth it to me.

I don't leave the house without this on my face. I'm a pale redhead and this sunscreen (and others by this brand) keeps me from getting burned. I spent a week in Mexico and wore only this brand of sunscreen---no burns at all.