Preventing and treating infection in minor cuts, scrapes, burns and surgical wounds. Some preparations are made as eye ointments for bacterial conjunctivitis and other surface eye infections.

The two attack the bacterium in different places, which is why they are paired. Polymyxin B punches into the outer membrane of Gram-negative bacteria so its contents leak out. Bacitracin blocks the carrier that ferries cell-wall building blocks into place in Gram-positive bacteria, so their wall cannot be completed.

Itching, redness or a rash where it is applied. An allergic contact dermatitis to bacitracin is well recognised and can look like the wound getting worse.

For external use only, on clean skin, and not on large areas, deep wounds or serious burns, where absorbed polymyxin B and bacitracin can affect the kidneys and hearing. Stop if the area becomes more red, itchy or swollen, which may be an allergy rather than the infection spreading. Do not use it for more than about a week without medical advice, and see a doctor for any wound with spreading redness, pus or fever.