Antiseptics & Disinfectants

Definitions & ideal properties

• Antiseptic — agent applied to living surfaces (skin, mucosa, wounds) to inhibit or kill microbes; low enough host-cell toxicity for direct application.
• Disinfectant — agent used on inanimate objects (instruments, surfaces, water); the antiseptic/disinfectant split is conventional (surface of application), not chemical — there is wide overlap, and a static-vs-cidal distinction between them is futile because action is concentration-dependent.
• Germicide — umbrella term for any agent that kills microbes (covers both antiseptics and disinfectants); sterilant = agent/process killing all microbes including spores.
• Disinfection vs sterilization — disinfection destroys most vegetative microbes and viruses but NOT spores; sterilization kills/removes ALL microorganisms including spores. Related: antisepsis, decontamination, sanitization, pasteurization (65–100 °C, non-sporulating organisms).
• Differ from systemic antimicrobials by low parasite selectivity — too toxic for systemic use. (Heralded by Semmelweiss — chlorinated-lime handwashing — and Lister — phenol antiseptic surgery.)

• Ideal properties — stable, cheap, non-staining; cidal not merely static (kills spores); broad-spectrum (bacteria/fungi/viruses/protozoa); brief contact time; spreads through organic films; active in blood, pus and exudates.
• Disinfectant — additional — should not corrode/rust instruments; easily washable.
• Antiseptic — additional — rapid with sustained (residual) protection; non-irritant; should not delay wound healing; non-absorbable/minimally toxic; non-sensitizing; compatible with soaps. Note: most topical antiseptics impair wound healing — soap-and-water may be less damaging.