Is H2O2 really a “natural” substance?
Yes. H2O2 is produced by both animal and plant cells — being associated with the mitochondrial respiratory chain, as well as various hydroxylation and oxygenation reactions. For example, the popular free-radical dietary supplement, superoxide dismutase (SOD), serves to convert the toxic superoxide radical (O2-) into H2O2, as do the flavin-linked oxidases. A number of other enzymes such as the heme-containing catalase (located in mitochondrial peroxisomes) then decompose the H2O2 to oxygen in order to protect the cells from subsequent damage. You can see these enzymes in action for yourself when you apply H2O2 topically to a cut or wound and witness the intense foaming. Also, the whitening of skin when exposed to more concentrated H2O2 is due to trapped oxygen beneath the epidermis caused as a result of H2O2 permeating through the skin and being decomposed by epidural enzymes. Saliva is another source for H2O2-decomposing enzymes — hence the foaming when brushing with H2O2-containing
