Benzalkonium chloride is a mixture of alkylbenzyl dimethylammonium chlorides of various alkyl chain lengths. It is commonly used as an antiseptic and spermicide. This product is a nitrogenous cationic surface-acting agent belonging to the quaternary ammonium group. The greatest bactericidal activity is associated with the C12-C14 alkyl derivatives. Benzalkonium chloride solutions are rapidly acting anti-infective agents with a moderately long duration of action. They are active against bacteria and some viruses, fungi, and protozoa. Bacterial spores are considered to be resistant. Solutions are bacteriostatic or bactericidal according to their concentration. Gram-positive bacteria are generally more susceptible than gram-negative. Activity is not greatly affected by pH, but increases substantially at higher temperatures and prolonged exposure times.