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. Both types cause sunburns and can ultimately lead to skin cancer. 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. Tinosorb S (Bis-ethyl-hexyloxyphenol methoxyphenyl triazine; BEMT; Bemotrizinol; Anisotriazine; Escalol S) is used in concentrations of 10%. It works to filter out both UVA and UVB rays. It also acts as a stabilizer for other filters within the sunscreen, especially avobenzone. It is fairly long-lasting on the skin (doesn’t dissolve in oil, but does in water) and doesn’t degrade in sunlight. Tinosorb is an ideal addition to broad spectrum sunscreens, but it is not currently available in the US or Canada. Keep in mind that a sunscreen’s Sun Protection Factor (SPF) is a gauge of how well the formula protects the skin from UVB rays. It does not gauge protection from UVA rays.