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What is conjunctivitis?

BMJ Group Medical Reference


If your eyes look red and feel gritty, you may have conjunctivitis. Conjunctivitis is an infection that affects your eyes. It usually clears up on its own after a few days, but it's a good idea to see a doctor or pharmacist, because occasionally it can be a sign of a more serious problem.

We've brought together the best research about conjunctivitis that's caused by germs called bacteria, and weighed up the evidence about how to treat it. You can use our information to talk to your doctor and decide which treatments are best for you.

Conjunctivitis is an infection of your conjunctiva. Your conjunctiva is the thin lining that covers the inside of your eyelids and the whites of your eyes.


If germs called bacteria infect your conjunctiva, it can become inflamed. This is called bacterial conjunctivitis. Your eyes look red and feel irritated, uncomfortable, and watery. You can also get thick pus coming from your eyes. [1] [2]

Lots of things, including dust, sand, and pollen, can irritate your eyes and make them inflamed. Viruses and allergies can also cause conjunctivitis. [1] [3]

If you have conjunctivitis caused by bacteria, you'll wake up with crusty eyelids. [2] [4] This is caused by pus coming from your eyes while you sleep. It's usually worse than the 'sleep' you normally have in your eyes when you wake up.

Conjunctivitis caused by viruses or bacteria can easily spread from person to person. You can help prevent this by:

  • Washing your hands often

  • Trying not to touch your eyes.

Conjunctivitis is very common among school children. Viruses and bacteria can spread from child to child when they play. [1] Children are also much more likely to get conjunctivitis if they already have an ear infection. The germs that cause ear infections and sinusitis can also cause conjunctivitis.

Adults are much more likely to get conjunctivitis if they tend to have very dry eyes. [5]

In about 65 in 100 people, conjunctivitis clears up on its own after a few days. [6] But conjunctivitis can occasionally be a sign of more serious eye problems, such as glaucoma, or an infection in your eyelid (a stye). And the infection that causes the conjunctivitis can sometimes get worse and spread if it isn't treated. [1]

Your doctor probably won't do tests to find out if your conjunctivitis is caused by bacteria. This is because the conjunctivitis usually clears up before the test results come back. Some doctors treat all people with conjunctivitis with antibiotic eye drops or ointment. Other doctors only treat conjunctivitis with antibiotics if they think it's been caused by bacteria. [2]

Last Updated: March 13, 2013
This information does not replace medical advice.  If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.

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