UV filters are ingredients which protect skin and hair from the damaging effects of the ultraviolet radiation which forms part of sunlight. Humans need protection from two types of ultraviolet radiation that reach the surface of the earth: UV-A and UV-B:

• UV-A radiation has a wavelength of 320-400 nanometres. UV-A penetrates deeper into the skin than UV-B, thereby having a stronger effect on the dermis. It is claimed to be the main cause of skin aging. Ten times more UV-A reaches the Earth's surface than UV-B. UV-A radiation produces damage to cellular proteins, lipids and carbohydrates. Although DNA absorption of UV-A is weak, it can cause structural changes in the DNA molecule (crosslinking). The UV-A band is divided into two subsets: UV-A II (320-340 nanometres) and UV-A I (340-400 nanometres). Research suggests that UV-A II (320-340 nm) in the most damaging to blood vessels.
  

• UV-B radiation has a wavelength of 290-320 nanometres. It does not penetrate as deeply into the skin, but is energy-rich and is responsible for causing sunburn, also called erythema.

Both types of UV radiation can cause skin cancer due to damage to DNA. They are suspected to affect the Langerhan cells in the epidermis and, therefore, the immunologic defense.

UV filters are ingredients which absorb, reflect, scatter and block ultraviolet radiation. They are also used as stabilizers, to protect the integrity of the finished products (color and fragrance). DSM Nutritional Products produces and markets UV-A and UV-B filters under the trade name PARSOL®.