Antiseptics, disinfectants, and antibiotics can be referred to as chemical anti-microbial agents, in contrast to physical antimicrobial agents such as heat and radiation. Microbiologists usually distinguish between antiseptics and disinfectants in the following way. Antiseptics are preparations of chemicals that are meant to be applied to the skin or other living tissue. Examples are chemical preparations designed to treat wounds or infected throats. Alcohol, probably the most widely used antiseptic, denatures proteins, extracts lipids, and dehydrates cells, all of which probably contribute to the effectiveness of alcohol as an antiseptic. Iodine is another excellent antiseptic, though its effects on microbes are not understood. Heavy metals are also used in antiseptic preparations; for example, laws require that silver nitrate be applied to the eyes of newborn humans, especially to prevent the transmission of gonococci from mother to infant.

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