Surfactants (Surface Active Agents) are compounds that reduce the surface tension of solvents such as water by decreasing the attraction between molecules.

Soaps and detergents are the most common surfactants.  Soaps have both a hydrophobic fatty acid region and a hydrophilic region.  The hydrophobic region breaks up lipids, while the hydrophilic region attracts water to wash the oils and bacteria away.  Though soaps are good degerming agents, they have very low antimicrobial activity unless antimicrobial compounds such as trichlosan are added.

Synthetic detergents such as quartenary ammonium compounds (quats) are positively-charged organic surfactants associated with ammonium ions.  These agents are more soluble in water than soaps and function by disrupting plasma membranes.  Quats are bacteriocidal, fungicidal and inactivate enveloped viruses, but are not effective against nonenveloped viruses, endospores or mycobacteria.  They are also harmless to human tissue, so are often used mouthwashes and oral rinses.  Examples include benzalkonium chloride (Zephiran) and cetylpyridium chloride (Cepacol).  Since quats are inactivated by soaps and other organic compounds and ineffective against some G- microbes such as Pseudomonas aeruginosa, they are considered low-level disinfectants.