Which compound has the formula H₂O₂ and is used as a household antiseptic?

The compound with the formula H₂O₂ used as a household antiseptic is hydrogen peroxide.

Each hydrogen peroxide molecule contains two hydrogen atoms and two oxygen atoms. It resembles water’s formula but has one additional oxygen atom, giving it different chemical properties. Pure hydrogen peroxide is a pale blue liquid, although household products are usually dilute and appear colorless.

Hydrogen peroxide decomposes into water and oxygen, especially in the presence of light, heat or catalysts such as the enzyme catalase. This decomposition explains its bubbling action on some biological materials. Household antiseptic solutions are commonly much more dilute than industrial preparations.

Hydrogen peroxide is also used for bleaching, wastewater treatment and chemical manufacture. It is not the same as chlorine bleach, whose active compound is commonly sodium hypochlorite. Concentrated hydrogen peroxide can be hazardous and is not equivalent to ordinary water.