Chloride peroxidase oxidises chloride in the presence of hydrogen peroxidase to form hypochlorous acid. This acid is the final product of the reaction in the absence of a suitable nucleophilic acceptor. However, it can go on to form a diversity of halogenated reaction products if a convenient nucleophilic acceptor is present.

Hypochlorous acid is strongly bacteriocidal and a powerful oxidising agent. It is secreted by pathogenic fungi e.g. Curvularia inaequalis in a mechanism to oxidise plant cell walls to facilitate penetration of the fungus into the host amongst other uses. It can also act upon Br- and I-.