How does an antiseptic differ from an antibiotic?

Answer 1

Antiseptic: of, relating to, or denoting substances that prevent the growth of disease-causing microorganisms. • (of medical techniques) based on the use of such substances.

Antibiotic: a medicine (such as penicillin or its derivatives) that inhibits the growth of or destroys microorganisms.

In short, antibiotics kill bacteria, whereas antiseptics merely inhibit make it harder for them to grow. (Both are designated as "antimicrobials".)

Answer 2

Antiseptic is only to local use. Antibiotic is to systemic use.
Classically antibiotic is a antibacterial substance of fungal origin.