High Quality Content by WIKIPEDIA articles! A photooxygenation is a light-induced oxidation reaction in which molecular oxygen is incorporated into the product(s). Initial research interest in photooxygenation reactions arose from Oscar Raab`s observations in 1900 that the combination of light, oxygen and photosensitizers is highly toxic to cells. Early studies of photooxygenation focused on oxidative damage to DNA and amino acids, but recent research has led to the application of photooxygenation in organic synthesis and photodynamic therapy.