Mupirocin is an antibiotic. It kills the bacteria that cause skin infections by preventing the synthesis of essential proteins necessary for survival of bacteria. Thus, it prevents the skin infection from spreading. Mupirocin is an antibiotic that works by stopping the growth of infection-causing bacteria on your skin. It prevents the synthesis of essential proteins necessary for the survival of bacteria. It is effective against skin infections such as boils, impetigo, and infected hair follicles. It may also be used to treat infections in small cuts or wounds on your skin. This treatment has few common side effects and should clear up infections within a few days, but you should keep using it for as long as it is prescribed.