Bacitracin is very safe. However, getting bacitracin in your eyes may cause redness and some pain and itching.
Intentionally eating bacitracin in large amounts may cause you to have some pain in your stomach and possibly throw up.
Rarely, bacitracin may cause an allergic reaction. You are most likely to have some redness and itching of your skin during a reaction. However, as with any substance a severe allergic reaction (anaphylaxis) can occur.
Bacitracin is still used as a body-wide (systemic) antibiotic in parts of the world. If it is given by injection, it may cause pain in the area of the shot, skin rash, nausea, vomiting, and bone marrow and kidney failure.
People who are sensitive to neomycin, another topical antibiotic, may react similarly to bacitracin.