I am not entirely sure what you mean by 'organic' sunscreen.Organic molecules are typically just comprised of carbon, nitrogen,and oxygen. These molecules would not be terribly great at absorbing UV rays, which are the primary cause of skin cancers, because they are not as stable under those conditions. Also, they can have potentially bad side effects as well. If you mean 'organic' like you have organic foods, then I think that the organic sunscreens can be very effective. The active ingredient in sunscreen is usually a mineral, such as ZincOxide or Titanium Dioxide that is dispersed in a lotion-like liquid.These minerals are "inorganic", but the lotion that they are dispersed in can be made out of all natural products, without bad chemicals.Zinc oxide and Titanium dioxide are also found naturally and do not pose any immediate threat to humans.