Erythromycin eye ointment is an antibiotic used to treat bacterial eye infections and to protect newborns from serious eye infections at birth. It comes as a 0.5% ointment applied directly to the eye and is one of the most commonly prescribed ophthalmic antibiotics in the United States.
Treating Bacterial Eye Infections
The primary use of erythromycin eye ointment is treating superficial bacterial infections of the eye, most commonly bacterial conjunctivitis (pink eye). It works by stopping bacteria from producing the proteins they need to grow and multiply, which halts the infection without damaging your own cells.
The ointment is effective against a broad range of bacteria that commonly cause eye infections. These include staph bacteria (a frequent culprit in pink eye and eyelid infections), strep bacteria, and several others that cause conjunctivitis or corneal infections. It also works against chlamydia, the bacterium responsible for a specific type of eye infection in both newborns and adults. One notable gap: MRSA (methicillin-resistant staph) is uniformly resistant to erythromycin, so it won’t help if that particular strain is causing the infection.
It’s worth knowing that resistance to erythromycin has been growing. A 2025 study in the journal Cornea found that gram-positive bacteria, the type most often behind eye infections, showed high levels of resistance to erythromycin. This doesn’t mean the ointment won’t work for your infection, but it does explain why your doctor may choose a different antibiotic if your symptoms aren’t improving after a few days of treatment.
Protecting Newborns at Birth
The other major use for erythromycin eye ointment is preventing a condition called ophthalmia neonatorum, a potentially sight-threatening eye infection that newborns can develop from bacteria in the birth canal, particularly gonorrhea and chlamydia. A single ribbon of ointment is placed in each of the baby’s eyes within the first 24 hours of life.
This practice is required by law in most U.S. states, and the U.S. Preventive Services Task Force recommends it for all newborns regardless of delivery method (vaginal or cesarean). Erythromycin is the only ophthalmic ointment recommended for this purpose in the United States. The CDC notes it remains the standard because of its safety, low cost, and ease of use. A fresh tube is used for each infant to prevent contamination.
That said, the conversation around universal newborn prophylaxis is shifting. The American Academy of Pediatrics issued a 2024 policy statement supporting “ongoing re-evaluation” of whether every baby truly needs the treatment and recommending it specifically in regions where gonorrhea is prevalent and routine prenatal screening can’t be guaranteed, or where state law still requires it.
How to Apply the Ointment
For treating an eye infection, the typical application is a 1-centimeter strip (about half an inch) of ointment placed inside the lower eyelid, up to six times daily depending on how severe the infection is. Here’s how to do it cleanly:
- Wash your hands thoroughly with soap and water before and after application.
- Pull down your lower eyelid with one finger to create a small pocket between the lid and your eye.
- Squeeze a half-inch ribbon of ointment into that pocket, keeping the tube tip close to but not touching your eye.
- Close your eyes gently for one to two minutes to let the medication absorb. Don’t blink hard or rub.
- Wipe away excess ointment from your eyelids and lashes with a clean tissue.
A mirror helps, or you can have someone else apply it. The key rule: never let the tube tip touch your eye, your fingers, or any surface. Contaminating the tip can introduce new bacteria into the tube and reinfect your eye with each application.
Side Effects and What to Expect
Erythromycin ointment is well tolerated. The most common side effects are minor: temporary blurred vision (the ointment is greasy, so this is expected), mild stinging or irritation when you first apply it, and slight redness. These typically resolve within minutes. Because of the blurred vision, many people prefer to apply the ointment right before bed.
True allergic reactions are uncommon but possible. If you notice increasing redness, swelling, itching, or a rash around your eyes that seems to be getting worse rather than better, stop using the ointment and contact your doctor.
Storage and Handling
Store the tube at room temperature, between 68°F and 77°F. Keep it away from excessive heat and don’t let it freeze. The manufacturer labeling does not specify how long the ointment remains stable after opening, so follow whatever timeline your pharmacist or doctor provides. If the ointment changes color, consistency, or smell, discard it.