Active Ingredients for Sunscreens and Sunblocks

The principal ingredients in sunscreens are usually aromatic molecules conjugated with carbonyl groups. This general structure allows the molecule to absorb high-energy ultraviolet rays and release the energy as lower-energy rays, thereby preventing the skin-damaging ultraviolet rays from reaching the skin.

So, upon exposure to UV light, most of the ingredients (with the notable exception of avobenzone) do not undergo significant chemical change, allowing these ingredients to retain the UV-absorbing potency without significant photodegradation. A chemical stabilizer is included in some sunscreens containing avobenzone to slow its breakdown – examples include formulations containing Helioplex and AvoTriplex. The stability of avobenzone can also be improved by bemotrizinol, octocrylene and various other photostabilisers.

Some sunscreens also include enzymes like photolyase, which are claimed to be able to repair UV-damaged DNA.