Erythromycin ophthalmic ointment is a topical antibiotic used to treat bacterial eye infections and to prevent eye infections in newborns. It works by stopping bacteria from producing the proteins they need to multiply, which halts the infection and lets the body clear it. It’s one of the most commonly prescribed eye ointments, available in a 0.5% concentration, and it’s the only eye ointment recommended for routine use in newborns in the United States.
How It Fights Bacterial Infections
Erythromycin belongs to a class of antibiotics called macrolides. It binds to a specific part of bacterial cells responsible for assembling proteins, effectively shutting down the machinery bacteria need to grow and reproduce. Rather than killing bacteria outright, it stops them from multiplying, giving your immune system the advantage it needs to eliminate the infection.
The ointment penetrates the cell walls of certain bacteria more easily than others. It’s especially effective against gram-positive bacteria (a broad category that includes staph and strep species), which can absorb up to 100 times more of the drug than gram-negative bacteria. This makes it a strong choice for many common eye infections, though it won’t work against every type of bacterium.
Common Uses in Adults and Children
For adults and older children, erythromycin ophthalmic ointment is primarily prescribed for superficial bacterial eye infections, including bacterial conjunctivitis (pink eye) and infections of the eyelid margins. The standard approach is to apply a ribbon of ointment about 1 centimeter long directly into the lower eyelid of the affected eye, up to six times daily depending on how severe the infection is. Your prescriber will tell you how long to continue treatment, but it’s important to finish the full course even if symptoms improve early.
The ointment is not effective against viral or allergic conjunctivitis, which are far more common causes of pink eye in adults. If your symptoms don’t improve after a few days of use, the cause may not be bacterial.
Why Newborns Receive It at Birth
If you’ve recently had a baby, you likely saw a nurse apply a small strip of ointment to your newborn’s eyes shortly after delivery. This is a routine preventive measure required by law in most U.S. states. The purpose is to protect against ophthalmia neonatorum, a serious eye infection that newborns can develop if they’re exposed to gonorrhea or chlamydia bacteria during birth.
The CDC recommends that every newborn receive erythromycin 0.5% ophthalmic ointment in both eyes as soon as possible after delivery, regardless of whether the birth was vaginal or cesarean. If the ointment isn’t given in the delivery room, hospitals are expected to administer it within 24 hours. Left untreated, gonococcal eye infections in newborns can cause corneal damage and even blindness, so this simple preventive step carries significant benefit for very little risk.
Erythromycin is the only ophthalmic ointment currently recommended for this purpose in the U.S. During past shortages, alternatives like injectable antibiotics or other eye drops were considered, but none matched erythromycin’s combination of safety, low cost, and ease of use for newborns.
Side Effects
Most people tolerate the ointment well. The most common side effects are mild and temporary: redness, stinging or burning in the eye, and itching at the application site. These typically resolve on their own within minutes.
Because it’s an ointment rather than a liquid drop, it will blur your vision for a few minutes after each application. This is normal and happens because the greasy base of the ointment coats the surface of the eye. Plan to avoid driving or any activity requiring sharp vision right after applying it.
In rare cases, erythromycin can cause eye irritation that wasn’t present before treatment started. Prolonged use of any antibiotic ointment also carries a small risk of encouraging the overgrowth of organisms that aren’t affected by the drug, including fungi. If your symptoms worsen or change during treatment, that’s worth reporting to your prescriber.
How to Apply It
Tilt your head back slightly and pull down your lower eyelid to create a small pocket. Squeeze a thin ribbon of ointment (about 1 centimeter, roughly the width of your fingernail) into that pocket. Close your eye gently and roll your eyeball around to spread the ointment across the surface. Avoid touching the tip of the tube to your eye, fingers, or any other surface, as this can introduce bacteria into the tube and contaminate the remaining ointment.
Store the tube at room temperature, between 68°F and 77°F. Keep it away from excessive heat and don’t let it freeze. Replace the cap tightly after each use.
Who Should Not Use It
The ointment is contraindicated for anyone with a known allergy to erythromycin. If you’ve had a reaction to other macrolide antibiotics in the past, let your prescriber know before using it. While erythromycin ophthalmic ointment is considered safe enough for routine newborn use, pregnant and breastfeeding individuals should use it only when clearly needed, as a general precaution that applies to most medications in this category.