Higher than normal levels of Hydrogen peroxide (H2O2) in the skin has been linked to depigmentation. Catalase seems to protect the melanin producing cells from oxidation damage caused by excess H2O2. This is the principle behind the use of pseudocatalase cream.
I wondered if there was some way of increasing the catalase in the body through diet, and I found some info.
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A study published in Nature found that hydrogen peroxide plays a role in the immune system. Scientists found that hydrogen peroxide is released after tissues are damaged in zebra fish, which is thought to act as a signal to white blood cells to converge on the site and initiate the healing process. When the genes required to produce hydrogen peroxide were disabled, white blood cells did not accumulate at the site of damage. The experiments were conducted on fish; however, because fish are genetically similar to humans, the same process is speculated to occur in humans. The study in Nature suggested asthma sufferers have higher levels of hydrogen peroxide in their lungs than healthy people, which could explain why asthma sufferers have inappropriate levels of white blood cells in their lungs.