Pyrithione

Pyrithione is an organosulfur heterocyclic compound that is used commercially as an antimicrobial agent. The term most commonly refers to zinc pyrithione, the zinc salt of pyrithione, which is widely used in consumer products to control fungal and bacterial growth. Zinc pyrithione is a staple in many anti-dandruff shampoos and is also found in certain soaps, creams, and deodorants, as well as in paints, coatings, and textiles to inhibit mildew and odor-causing organisms.

Pyrithione compounds exhibit broad-spectrum antimicrobial activity, notably against yeasts such as Malassezia and various bacteria. The exact mechanism is not fully understood, but it is thought to involve disruption of cell membranes and interference with essential enzymatic processes that rely on metal ions. The zinc salt form increases lipophilicity and helps deliver the active compound to microbial cells.

In use, zinc pyrithione is typically formulated at low concentrations appropriate for topical exposure, often in the low single-digit percent range in shampoos. It is generally considered safe when used as directed, but can cause skin irritation or allergic contact dermatitis in sensitive individuals and may be harmful to aquatic life in high concentrations. Regulatory agencies regulate permissible levels in cosmetics and domestic products, and manufacturers provide usage guidelines to minimize risk.