Photocarcinogen
Encyclopedia
A photocarcinogen is a substance which causes cancer following illumination. This destructive effect often results from free radicals generated by the photocarcinogen. Many chemicals that are not carcinogenic can be photocarcinogenic. This can easily be understood from a photochemical perspective: The reactivity of a chemical substance itself might be low, but after illumination it transfers to the excited state. This excited state is chemically much more reactive and therefore potentially harmful to biological tissue.

Melanin
Melanin
Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...

 is not a photocarcinogen, because it dissipates the excitation energy into small amounts of heat (see photoprotection
Photoprotection
Photoprotection is a group of mechanisms that nature has developed to minimize the damage that the human body suffers when exposed to UV radiation...

). Oxybenzone
Oxybenzone
Oxybenzone is an organic compound used in sunscreens. It forms colorless crystals that are readily soluble in most organic solvents. A 2008 study by the US Centers for Disease Control and Prevention found the compound to be present in 96.8% of human urine samples analyzed as part of the...

 (a component of some sunscreen
Sunscreen
Sunblock is a lotion, spray, gel or other topical product that absorbs or reflects some of the sun's ultraviolet radiation on the skin exposed to sunlight and thus helps protect against sunburn...

s) is suspected owing to its skin penetrating qualities and its production of free radicals.
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