How can i prevent skin darkening from sun exposure?

Physical sunblock: The use of a good quality physical sun block that blocks out both UV A and UVB rays. The skin will still tan but to a much lesser extent. The physical block should be either zinc or titanium . Theses products can be purchased at a dermatologist office and in many spas. The better products are PCA, Skin Medica, SkinCeuticals, Obagi and others but these are most popular