Antiseptics and disinfectants cannot be used as antibiotics, as they do not have the selectivity necessary to prevent damage to the patient.
It is possible to use antiseptics externally, on a patient’s skin. This allows for wounds to be cleaned, reducing the likelihood of an infection.
Disinfectants are used on inanimate objects, such as countertops and door handles. This can reduce the likelihood of an infection being obtained from these fomites.
Good disinfectants and antibiotics are good at killing bacteria, viruses, and protozoa. However, their poor selectivity also means they are good at killing eukaryotic cells – this is not a desirable feature of an antibiotic. Therefore, they cannot be used externally.