Pink eye can be a bacterial infection, but most of the time it isn’t. The most common cause of pink eye is actually a virus, particularly adenovirus. Bacteria, viruses, and allergens can all cause conjunctivitis, and each type looks and feels a little different. Knowing which one you’re dealing with matters because the treatment is not the same.
What Causes Pink Eye
Viral infections account for the majority of pink eye cases. Bacterial infections are the second most common cause, followed by allergies. In babies, an incompletely opened tear duct can also produce symptoms that look like pink eye.
When bacteria are the cause, the specific culprits depend on your age. In children, the infection is often caused by common respiratory bacteria, the same types responsible for ear infections and sinus infections. In adults, chronic cases tend to involve staph bacteria. Sexually transmitted bacteria can also cause conjunctivitis, and these cases tend to be more aggressive, producing heavy discharge and requiring prompt treatment.
How to Tell Bacterial Pink Eye Apart
The biggest clue is the discharge. Bacterial pink eye produces thick pus that often causes your eyelids to stick together, especially when you wake up in the morning. You might need to gently clean your eyelids apart with a warm, wet washcloth before you can fully open your eyes.
Viral pink eye, by contrast, produces a watery, thinner discharge. It often starts in one eye and spreads to the other within a day or two, and it frequently accompanies a cold or upper respiratory infection. Both types cause the hallmark pink or red color in the white of the eye from swollen blood vessels, so redness alone won’t tell you which type you have.
Allergic conjunctivitis usually affects both eyes at once, causes intense itching, and tends to come alongside other allergy symptoms like sneezing and a runny nose. It’s not contagious.
Does Bacterial Pink Eye Go Away on Its Own?
Mild bacterial pink eye often resolves without antibiotics. It typically clears up in 2 to 5 days without treatment, though it can linger for up to 2 weeks before it’s completely gone. Antibiotics can speed recovery and reduce the chance of spreading it to others, but they aren’t always necessary for straightforward cases.
Your doctor may prescribe antibiotic eye drops or ointment if symptoms are moderate, if you wear contact lenses, or if the infection shows no signs of improving after a few days. More aggressive bacterial infections, particularly those caused by sexually transmitted bacteria, do require prompt antibiotic treatment to prevent damage to the eye.
How Long You’re Contagious
Bacterial pink eye is contagious from the moment symptoms appear until about 48 hours after starting antibiotic treatment. If you don’t use antibiotics, you remain contagious as long as symptoms persist. Viral pink eye is contagious for even longer, sometimes up to two weeks.
Both types spread easily through direct contact with eye discharge or contaminated surfaces. Touching your infected eye and then touching a doorknob, towel, or another person’s hand is all it takes.
Preventing the Spread
Handwashing is the single most effective way to stop pink eye from moving through a household. Wash with soap and water for at least 20 seconds, and do it before and after touching your eyes, applying eye drops, or cleaning discharge. If you don’t have soap available, hand sanitizer with at least 60% alcohol works.
Beyond handwashing, a few practical steps make a real difference:
- Don’t share personal items. Pillowcases, towels, washcloths, eye drops, makeup, and eyeglasses should all stay with one person.
- Clean discharge frequently. Use a fresh, wet washcloth or cotton ball each time you wipe your eyes, and throw cotton balls away after a single use.
- Wash fabrics in hot water. Pillowcases, sheets, towels, and washcloths should go through the laundry with hot water and detergent.
- Stop wearing contact lenses. Switch to glasses until your symptoms are fully gone. Throw away disposable lenses and cases you used while infected, and thoroughly clean reusable lenses and cases.
- Keep your hands away from your face. If you have pink eye in one eye, touching it and then touching the other eye can spread the infection to both.
- Use separate eye drop bottles. Don’t use the same bottle for your infected and uninfected eye.
If someone in your household has pink eye, avoid touching items they’ve used and wash your hands immediately after any contact with their belongings, whether that’s applying their eye drops or handling their bedding.