Antiseptic is a substance that destroys--or stops the growth of--germs on living tissue. Antiseptics are applied to skin and mucous membranes to help prevent infection. They must be strong enough to fight germs but mild enough not to irritate sensitive tissues. Antiseptics differ from disinfectants and antibiotics. Disinfectants are chemicals that destroy germs on nonliving objects, and antibiotics are drugs that treat infection after it occurs.