Many of us put on sunscreen to avoid the harmful effects of the sun, with the biggest concern being skin cancer. Skin cancer has become more prevalent in the last decade or so and more cases are being caught early enough so that the cancer can be removed without further problems. You may ask what is the difference between "sun block" and "sunscreen". Sun block is more of a marketing term given to sunscreen, although no sunscreen is able to completely protect your skin from those harmful rays of the sun. Even the highest levels of SPF sun protection factor) will still let some of the harmful rays through. As for SPF, many consumers are confused as to how much better SPF 30 is than say SPF 15. Is it double the protection No, an SPF 15 will block 93% of UVB rays, while SPF 30 blocks just 4% more Anything higher than a SPF 30 rating does not give you any better protection from UV rays. Ultimately, you need a sunscreen or sun block that blocks out the vast majority of UVB as well as UVA rays. Thanks for sharing with us.