As there are many sunscreens available on the market it may be difficult to determine which to use. Most sunscreens are effective at blocking UVB, but UVA is much more difficult to defend against. Neutrogena is my preference as it offers excellent UVA protection as well as UVB protection. I typically recommend an SPF 30 or higher for my patients and urge them to reapply it every two hours when exposed to the sun.
Web reference: http://www.perridermatology.com