Benzophenone-4, also known as sulisobenzone, is an ingredient used in sunscreens to protect the skin from damage by UVA and UVB rays. Benzophenone-4 is classified as a chemical sunscreen ingredient. Chemical sunscreens protect the skin by first absorbing UV light, then transforming that light energy into some other form of energy, such as heat. This is in contrast to physical sunscreens which protect the skin by using physical UV filters to block or deflect UV light.
A benefit of chemical sunscreen ingredients like benzophenone-4 is their ability to defend the deeper layers of skin, including collagen fibers and other tissue, against the aging effects of UVA rays, as well as preventing penetration by the UVB rays responsible for tanning and sunburn. A drawback of chemical sunscreens, however, is that they rub off more easily since they are thinner and must be reapplied more frequently. Benzophenone-4 has also been associated with skin and eye irritation.