Asepsis is the practice to reduce or eliminate contaminants (such as bacteria, viruses, fungi, and parasites) from entering the operative field in surgery or medicine to prevent infection. Ideally, a field is "sterile" — free of contaminants — a situation that is difficult to attain. However, the goal is elimination of infection, not sterility.
Antiseptis is a term used sometimes as a synonym, but also applies to the uses of antiseptics. Antiseptics are agents that reduce or kill germs chemically and are applied to skin and wound surfaces. In contrast, disinfectants are chemicals applied to inert surfaces and are usually too harsh to be used on biological surfaces. Antibiotics kill specifically bacteria and work biochemically; they can be used externally or internally.
The first step in asepsis is cleanliness, a concept already espoused by Hippocrates. The modern concept of asepsis evolved in the 19th century. Semmelweis showed that washing the hands prior to delivery reduced puerperal fever. After the suggestion by Louis Pasteur, Lister introduced the use of carbolic acid as an antiseptic and reduced surgical infections rates. Lawson Tait went from antisepsis to asepsis, introducing principles and practices that have remained valid to this day. Ernst von Bergmann introduced the autoclave, a device used for the sterilization of surgical instruments.
Today's techniques include a series of steps that complement each other. Foremost remains good hygienic practice. The procedure room is laid out according to specific guidelines, subject to regulations concerning filtering and airflow, and kept clean between surgical cases. A patient who is brought for the procedure is washed and wears a clean gown. The surgical site is washed, possibly shaved, and skin is exposed to a germicide (i.e., an iodine solution such as betadine). In turn, members of the surgical team wash hands and arms with germicidal solution. Operating surgeons and nurses wear sterile gowns and gloves. Hair is covered and a surgical mask is worn. Instruments are sterilized through autoclaving, or, if disposable, are used once. Irrigation is used in the surgical site. Suture material or xenografts have been sterilized beforehand. Dressing material is sterile. Antibiotics are often not necessary in a "clean" case, that is, a surgical procedure where no infection is apparent; however, when a case is considered "contaminated," they are usually indicated.
Dirty and biologically contaminated material is subject to regulated disposal.