Zinc pyrithione

Overview
Zinc pyrithione is chemical compound used as an antifungal and antibacterial agent. This coordination complex, which has many names, was first reported in the 1930s. It features two pyridine-derived chelating ligands bound to zinc via oxygen and sulfur atoms.

Medical
Zinc pyrithione is best known for its use in treating dandruff and seborrheic dermatitis. It also has antibacterial properties and is effective against many pathogens from the streptococcus and staphylococcus class. Its other medical applications include treatments of psoriasis, eczema, ringworm, fungus, athletes foot, dry skin, atypical dermatitis, tinea, and vitiligo.

Zinc pyrithione is approved for over-the-counter topical use in the United States as a treatment for dandruff. It is the active ingredient in several anti-dandruff shampoos such as Head & Shoulders. However, in its industrial forms and strengths, it may be harmful by contact or ingestion.

In paint
Due to its low solubility in water (8 ppm at neutral pH), zinc pyrithione is suitable for use in outdoor paints and other products that provide protection against mildew and algae. It is an effective algaecide. It is chemically incompatible with paints relying on metal carboxylate curing agents. When used in latex paints and the water contains high amount of iron, a sequestering agent that will preferentially bind the iron ions is needed. Its decomposition by ultraviolet light is slow, providing years of protection even against direct sunlight.

Mechanism
Its antifungal effect most likely lies in the ability of an un-ionized pyrithione molecule to disrupt membrane transport by blocking the proton pump that energizes the transport mechanism. Fungi are capable of inactivating pyrithione in low concentrations.