An antiseptic is a substance that is applied to lesions or wounds of the skin to kill germs. This helps prevent the wound becoming infected. Commonly used antiseptics include alcohol, iodine and mercury compounds. Antiseptics are different from antibiotics. Antiseptics can only be used on the skin, antibiotics can also be used internally, through the blood and lymphatic systems. They are also different from disinfectants: Disinfectants are used on non-living objects only, because they are dangerous to the living.