Understanding the active ingredients in sunscreen is a bit like learning a foreign language that uses a different alphabet. Suffice it to say in short that sunscreens are made up of a combination of two types of ingredients: those that reflect ultraviolet (UV) rays and those that absorb UV rays. Although that might sound simple enough, there are also two types of rays: UVA rays and UVB rays. UVB causes sunburn at the outer layers of skin, but UVA causes sun damage that reach deeper layers of skin. Both UVA and UVB radiation can contribute to the development of skin cancer. Most sunscreen ingredients protect against UVB rays, but bisdisulizole disodium, (also known as disodium phenyl dibenzimidazole tetrasulfonate or DPDT) absorbs UVA radiation. It is not approved in the United States or Canada, but was approved in the European Union and other parts of the world a decade ago.