At a glance

What is bacitracin?

Bacitracin is an antibiotic that is actually a mixture of closely related cyclic polypeptides¹, produced by bacteria in the Bacillus subtilis² group. It is a peptide antibiotic rather than a small-molecule drug, and its main component, bacitracin A, is the most active.

It is used almost entirely on the skin. In the United States, it is widely available over the counter² as an ointment for minor wound care, both on its own and combined with other topical antibiotics.

The history of bacitracin

Bacitracin owes its name to a child. In 1945², researchers isolated the antibiotic-producing Bacillus strain from the wound of a seven-year-old girl named Margaret Tracy, and the drug's name combines "Bacillus" with "Tracy."

It arrived during the early antibiotic era, shortly after penicillin. Its toxicity when injected limited its use as a systemic drug, but it found a durable place as a topical antibiotic that is still sold today.

How does bacitracin work?

Bacitracin kills bacteria by blocking the construction of their cell wall. It interferes with a recycling step in wall-building: A lipid carrier¹ molecule (C55 or undecaprenyl pyrophosphate) ferries the building blocks of the wall across the bacterial membrane, and it must shed a phosphate to be reused. Bacitracin binds that carrier and prevents its dephosphorylation², so the carrier is pulled out of circulation and new cell-wall material can no longer be delivered.

Because this target matters most in gram-positive bacteria, bacitracin's activity is strongest against organisms such as staphylococci and streptococci. It is poorly absorbed through the skin, which is part of why it works well as a surface antibiotic but is not used orally for body-wide infection.

Is it FDA-approved?

Yes, and much of it is sold without a prescription. Its status depends on the form, and the injectable form is the exception:

What is bacitracin used for?

Bacitracin is used to prevent infection in minor skin wounds such as cuts, scrapes, and burns, and it is a common ingredient in first-aid ointments. It is frequently combined with neomycin and polymyxin B³ in "triple antibiotic" products to broaden the range of bacteria covered.

One nuance is worth knowing: for clean minor wounds, antibiotic ointment is not clearly better than plain petroleum jelly. In a randomized trial⁴ of 922 dermatologic-surgery patients, white petrolatum and bacitracin produced comparable, low infection rates, while only the bacitracin group had cases of allergic contact dermatitis. That has led many clinicians to favor plain petrolatum for routine wound care.

What are the side effects?

The most notable side effect of bacitracin is allergy. Its main risks are:

• Allergic contact dermatitis: it is a well-recognized cause of this itchy, red, sometimes blistering rash where it is applied, and in 2003⁵, the American Contact Dermatitis Society named it "Allergen of the Year."
• Anaphylaxis: more rarely, topical bacitracin has triggered anaphylaxis⁵, a severe whole-body allergic reaction, which is unusual for an over-the-counter ointment.
• Kidney damage: when given by injection, bacitracin can cause serious kidney damage², which is why that form was taken off the U.S. market.

Applied topically to small areas, it is generally well tolerated apart from the allergy risk.

More for skin & aging