The answer is alcohol. Antiseptics used directly on skin lean heavily on a high concentration of it.
Ammonium, formaldehyde, and sodium hypochlorite (bleach) are all disinfectant-grade chemicals — several of them would actually be unsafe to put on skin the way antiseptics are designed to be used. That's the real distinction: antiseptics are built for skin, disinfectants are built for tools and surfaces.
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