No evidence of safety

Hydrogen peroxide isn’t necessarily safe. It can cause harm in three ways: corrosive damage, the unwanted formation of oxygen gas, and by lipid peroxidation. At low concentrations, the risks of serious harms are remote. At high concentrations, peroxide is highly toxic. Peroxide can cause significant tissue damage. As a tooth whitener, it can irritates gums. When swallowed in larger volumes, it can cause nausea and vomiting. High concentrations of peroxide will cause mucosal burns. The secondary harm is due to oxygen release. Peroxide can cause an oxygen embolism in the bloodstream, which can cause strokes. In other body cavities, like the stomach, it can cause distension and painful gas. Deaths have been associated with injectable use – a “naturopath” was convicted of criminally negligent homicide for administering intravenous peroxide to a cancer patient that died the day after treatment. Lethargy, confusion, coma, cardiorespiratory arrest have been reported following consumption of hydrogen peroxide. Quackwatch has a nice summary of how the harm can