Yes, erythromycin ophthalmic ointment is used to treat pink eye, but only the bacterial form. It’s one of the most commonly prescribed topical antibiotics for bacterial conjunctivitis and works against a broad range of bacteria that cause eye infections. If your pink eye is caused by a virus or allergies, erythromycin won’t help.
How It Treats Bacterial Pink Eye
Erythromycin is a bacteriostatic antibiotic, meaning it stops bacteria from growing rather than killing them outright. It does this by blocking the machinery bacteria use to build proteins, which effectively halts their ability to multiply. Your immune system then clears the weakened infection on its own.
The ointment covers many of the bacteria most commonly responsible for eye infections, including staph, strep, and Haemophilus influenzae. It also works against Chlamydia trachomatis, which can cause a specific type of eye infection. No topical antibiotic has been shown to be superior to another for routine bacterial conjunctivitis, according to the American Academy of Ophthalmology, so erythromycin remains a standard option.
Why It Won’t Work for Every Type of Pink Eye
Pink eye has three main causes: bacteria, viruses, and allergies. Erythromycin only targets bacteria. Viral conjunctivitis, which is the most common form, will not respond to any antibiotic. Allergic conjunctivitis is an immune reaction to things like pollen or pet dander, and antibiotics have no role there either.
Using erythromycin when you don’t have a bacterial infection won’t speed up recovery and contributes to antibiotic resistance. The AAO specifically advises against indiscriminate use of topical antibiotics for this reason. Mild bacterial pink eye is also often self-limited, clearing up in 2 to 5 days without treatment, though it can linger for up to 2 weeks. Antibiotics shorten that timeline, reduce the risk of complications, and help you stop being contagious sooner.
Telling Bacterial Pink Eye Apart
Bacterial conjunctivitis tends to produce thick, yellow or green discharge that can crust your eyelids shut overnight. It often starts in one eye and spreads to the other within a day or two. Viral pink eye, by contrast, usually causes watery discharge and often accompanies a cold or upper respiratory infection. Allergic pink eye typically affects both eyes simultaneously with intense itching.
These distinctions aren’t always clear-cut, which is why a proper evaluation matters before starting an antibiotic ointment.
How to Apply the Ointment
The standard approach is to squeeze about 1 centimeter (roughly one-third of an inch) of ointment into the lower eyelid. Here’s the process:
- Wash your hands thoroughly before and after application.
- Tilt your head back and use your index finger to gently pull your lower eyelid down, creating a small pouch.
- Squeeze a thin strip of ointment into that pouch without letting the tube tip touch your eye, fingers, or any other surface.
- Close your eye gently and keep it closed for one to two minutes so the medicine can spread across the surface of the eye.
- Wipe the tube tip with a clean tissue afterward and recap it tightly.
You may need to apply it up to six times daily depending on how severe the infection is. The ointment will temporarily blur your vision after each application since it sits as a greasy film over the eye. Many people prefer to use it right before bed for this reason, or they pair it with antibiotic drops during the day.
What to Expect During Recovery
With antibiotic treatment, most cases of bacterial pink eye start improving within one to two days. The CDC notes that antibiotics help shorten the overall length of infection and reduce the chance of spreading it to others. You should finish the full course your provider prescribed even if symptoms clear up early, since stopping too soon can allow the infection to return.
If your symptoms aren’t improving after two to three days on the ointment, or if you notice worsening pain, sensitivity to light, or changes in your vision, those are signs the infection may need a different approach.
Its Other Role: Newborn Eye Protection
You may have heard of erythromycin ointment being applied to newborns’ eyes right after birth. This is a different use entirely. It’s given as a preventive measure against gonococcal ophthalmia neonatorum, a serious eye infection newborns can pick up during delivery. Erythromycin is the only FDA-approved drug for this purpose, and newborn eye prophylaxis is mandated in most U.S. states. This preventive application is a single dose at birth, not a treatment course for active pink eye.