Hydrogen peroxide can act as an oxidizing or reducing agent at different pH values, enabling its reaction with both metals and nonmetals, such as iron and fluorine respectively. Hydrogen peroxide is highly oxidizing in acidic solutions, outranking halogens and halogen compounds, such as fluorine and chlorine dioxide, in oxidation potential.
Hydrogen peroxide can also react in the presence of d-block catalysts to produce intermediate hydroxyl radicals possessing high reactivity. The compound oxidizes ferrous iron to ferric ion in acidic media.
The pH dependency of the compound is illustrated through its reaction with potassium permanganate. In acidic media, hydrogen peroxide reduces the magnesium (+4) ions of potassium permanganate to magnesium (+2) ions. In basic media, however, hydrogen peroxide oxidizes magnesium (+2) ions to magnesium (+4) ions.
The weak acidity of hydrogen peroxide enables it to form unstable hydroperoxide and peroxide salts with metals. It can also convert metal oxides to their respective peroxides. A reaction between hydrogen peroxide and borax produces the bleaching agent, sodium perborate, used in laundry detergents. The compound also reacts with urea, producing the teeth-whitening agent adduct hydrogen peroxide-urea.
Hydrogen peroxide reacts with the enzyme catalase in the blood, enabling it to decompose into water and oxygen gas. The white foam produced was thought to have antiseptic properties, a notion that was disproved by a study in the Journal of Family Medicine in 1987.