Yes, erythromycin ophthalmic ointment is one of the most commonly prescribed treatments for bacterial pink eye (conjunctivitis). It’s a macrolide antibiotic that works by killing the bacteria causing the infection, and it comes as a 0.5% ointment applied directly to the eye. That said, erythromycin only works on bacterial forms of pink eye, and most cases of pink eye in adults are actually viral, meaning the ointment won’t help.
Why It Only Works for Bacterial Pink Eye
Pink eye has three main causes: bacteria, viruses, and allergies. Erythromycin targets bacteria specifically, so it does nothing for viral or allergic conjunctivitis. This distinction matters because, according to the CDC, most acute conjunctivitis cases in adults are viral and self-limited. They clear up on their own without antibiotics.
The tricky part is that bacterial and viral pink eye look similar. Both cause redness, tearing, and discomfort. Bacterial conjunctivitis tends to produce thick, yellowish or greenish discharge that mats your eyelids together, especially after sleep. Eyelid swelling, pain, and decreased vision are also more typical of bacterial infections. Viral pink eye, by contrast, usually produces watery discharge and often follows a cold or upper respiratory infection. Your doctor uses these clues to decide whether erythromycin is appropriate, though the overlap in symptoms can make diagnosis difficult even for experienced clinicians.
The American Academy of Ophthalmology notes that mild bacterial conjunctivitis is often self-limited too, and that no single topical antibiotic has been shown to be superior to another. So erythromycin isn’t necessarily the “best” antibiotic for bacterial pink eye. It’s simply one well-established option among several.
How to Apply the Ointment
A standard course is a roughly 1 cm ribbon of ointment applied to the inside of the lower eyelid four times a day for seven days. In more severe infections, your doctor may recommend applying it up to six times daily. Here’s the correct technique:
- Wash your hands thoroughly before and after.
- Pull down your lower eyelid gently to create a small pocket.
- Squeeze a thin line of ointment (about half a centimeter) along the inside of that lower lid.
- Close your eye gently and keep it shut for about 30 seconds. Don’t rub.
- Avoid touching the tube tip to your eye, eyelid, or lashes. Recap immediately after use.
The ointment will temporarily blur your vision, which is normal. Many people prefer to apply it right before bed for this reason, though you’ll still need to use it during the day if your prescribed schedule calls for it.
What to Expect During Treatment
Symptoms typically start improving within a few days, but you should finish the entire course even if your eyes feel better. Stopping early can allow surviving bacteria to regrow, potentially leading to a harder-to-treat infection. If you don’t notice any improvement after a few days, or if your symptoms get worse, that’s a sign the infection may not be bacterial, or it may involve a resistant strain that needs a different approach.
The ointment is generally well tolerated. Some people experience minor irritation or stinging on application. Serious side effects are rare but can include signs of an allergic reaction like significant swelling, itching, or rash around the eye. If that happens, stop using it.
Erythromycin for Newborns
You may have heard that babies receive erythromycin ointment in their eyes right after birth. This is a separate, preventive use. Newborns can pick up gonorrhea bacteria from the birth canal, which can cause a severe eye infection called gonococcal ophthalmia neonatorum. Erythromycin is the only FDA-approved drug for preventing this condition, and the U.S. Preventive Services Task Force recommends it for all newborns with high certainty that the benefit is substantial. This is a single prophylactic application, not a treatment course like you’d use for pink eye.
When Erythromycin Isn’t the Right Choice
If your pink eye is caused by a virus, erythromycin won’t shorten the infection or reduce your symptoms. Viral conjunctivitis runs its course in one to three weeks, and treatment focuses on comfort measures like cool compresses and artificial tears. Allergic conjunctivitis, which tends to affect both eyes with intense itching, responds to antihistamine drops rather than antibiotics.
Even when the cause is bacterial, your doctor might choose a different antibiotic. Fluoroquinolone eye drops, for example, are another common option and have the advantage of being liquid drops rather than an ointment, which means less blurring. The choice often comes down to the severity of infection, your comfort preference, cost, and whether you wear contact lenses. Erythromycin ointment remains popular partly because it’s inexpensive, widely available, and has a long safety track record in both adults and children.