Introduction

Conjunctivitis, also known as pink eye, is an inflammation of the conjunctiva. This is a protective membrane that covers the visible white part of the eye and the inner side of the eyelid. Conjunctivitis makes the affected eye(s) turn red.

The inflammation is commonly caused by germs such as viruses or bacteria (infectious conjunctivitis). But it is also often caused by an allergy (allergic conjunctivitis).

It often affects both eyes because the infection can easily spread from one eye to the other. To prevent this from happening, it’s important to avoid touching an infected eye. If you do touch it, be sure to wash your hands right away. It is also a good idea to use your own towels and washcloths, and not share them with other people.

At a glance

• The protective membrane that covers the white part of the eye (conjunctiva) can become inflamed due to viruses, bacteria or an allergy.
• This causes your eye to turn red and watery. Your eyelids may stick together, especially in the morning.
• Conjunctivitis caused by viruses or bacteria usually goes away on its own, but it is contagious.
• It is important not to touch your eyes with your fingers or objects such as eye droppers.
• Antibiotic eye drops are only effective against bacterial infections.

Side view of the eye showing the conjunctiva (in red)

Symptoms

Bacterial conjunctivitis makes your eyes red and watery. The conjunctiva produces a yellowish-white discharge that makes your eyelids stick together. This is especially noticeable when you wake up in the morning. The conjunctiva can also become sore and hurt when you move your eye, and you may have an itching and burning sensation in your eyes.

Viral conjunctivitis has similar symptoms, but the eyes typically secrete a more watery fluid. The same applies whether one or both eyes are inflamed from either rubbing them too much or because of contact with a liquid irritant.

If conjunctivitis is caused by an allergy, both eyes are always affected. Here, too, the eyes water. Itching is a typical sign of an allergy. Allergic conjunctivitis is often accompanied by other allergy symptoms such as a runny nose.

Other symptoms, such as poor vision, increased sensitivity to light or the feeling that you have something in your eye are rare. But they may be signs of a more serious problem, especially if you also have a severe headache, nausea or vomiting. It is important to see a doctor fast if you have any of these symptoms.

Inflamed conjunctiva

Causes

Conjunctivitis is often caused by viruses or bacteria. Viral and bacterial conjunctivitis are both contagious. The germs are often transferred by touch, and the infection can spread from one eye to the other – for instance, if you touch both eyes with your fingers. But it can also spread through contact with objects such as eye drop bottles, tissues, washcloths or binoculars.

Another common cause of conjunctivitis is allergic reactions – for instance, to pollen, animal fur or dust mites. Conjunctivitis can also be caused by dust or dirt, dry air, irritating liquids or damage to the conjunctiva. Sometimes the eye isn't kept moist enough with tear fluid, and that can lead to conjunctivitis too. If conjunctivitis is caused by an allergy or another external factor, it is not contagious.

Outlook

Bacterial conjunctivitis usually doesn't have any serious consequences. In more than half of all people, it goes away without treatment within one to two weeks. Viral conjunctivitis often goes away on its own within a few weeks too.

Conjunctivitis can also become chronic. It is considered to be chronic if it lasts longer than four weeks.

Effects

In rare cases the infection can spread to the cornea (the transparent front surface of the eye). This is more likely to happen if you wear contact lenses. But the risk of keratitis (inflammation of the cornea) is quite small: Only about 3 out of 10,000 people who wear contact lenses develop keratitis after having conjunctivitis.

Diagnosis

If the doctor thinks you may have conjunctivitis, they will ask you about the typical symptoms (such as itching, the feeling that you have a foreign object in your eye, or sticky eyelids) and how long you have had these symptoms for. After that your eyes and eyelids will be examined for any possible injuries or external irritants.

It usually isn't possible to say whether conjunctivitis is bacterial or viral based on the symptoms alone. In rare cases, a sample of the eye discharge is taken to find out what type of germs the infection is being caused by. That could make sense if your doctor thinks you may have another disease based on additional symptoms. For instance, a burning sensation when you pee could be a sign of a sexually transmitted infection like gonorrhea, with the germs unknowingly being wiped into your eyes.

Treatment

Conjunctivitis typically clears up without treatment. While you are waiting for this to happen, you can try resting your eyes – for example, by not working a lot in front of a screen. Hygiene is also important, like washing your hands regularly: That can help to prevent infecting your other eye if it is still healthy and keep other people from getting conjunctivitis.

Some people use cold or lukewarm compresses to relieve the symptoms. Others use eye drops to moisten the inflamed eye. But there has not been enough research on how effective these measures are, or whether they could even be harmful.

Medication is suitable for use once it is clear what kind of conjunctivitis you have: If an allergy is the cause, it can be treated with allergy medicine such as antihistamines. If your conjunctivitis is bacterial, antibiotic eye drops or creams can help make it go away a bit faster. But antibiotics are only effective against bacteria, and have no effect on viruses. If the infection is viral, only the symptoms can be treated.

Further information

When people are ill or need medical advice, they usually go to see their family doctor first. If you have conjunctivitis, your family doctor or pediatrician can tell whether it is a good idea to go to an eye doctor too. They will also be able to decide how long you need to rest at home so that your eyes can rest and you don't infect anyone else in school or at work.

Information about health care in Germany can help you to navigate the German healthcare system and find a suitable doctor. You can use this list of questions to prepare for your appointment.

Sources

• Azari AA, Arabi A. Conjunctivitis: A Systematic Review. J Ophthalmic Vis Res 2020; 15(3): 372-395. [PMC free article: PMC7431717] [PubMed: 32864068]
• Berufsverband der Augenärzte Deutschlands (BVA), Deutsche Ophthalmologische Gesellschaft (DOG). Leitlinie Nr. 12: Bakterielle Konjunktivitis. 2011.
• Castillo M, Scott NW, Mustafa MZ et al. Topical antihistamines and mast cell stabilisers for treating seasonal and perennial allergic conjunctivitis. 2015; (6): CD009566. [PMC free article: PMC10616535] [PubMed: 26028608]
• Chen YY, Liu SH, Nurmatov U et al. Antibiotics versus placebo for acute bacterial conjunctivitis. Cochrane Database Syst Rev 2023; (3): CD001211. [PMC free article: PMC10014114] [PubMed: 36912752]
• Epling J. Bacterial conjunctivitis. BMJ Clin Evid 2012; 20: 0704. [PMC free article: PMC3635545] [PubMed: 22348418]
• Liu SH, Hawkins BS, Ng SM et al. Topical pharmacologic interventions versus placebo for epidemic keratoconjunctivitis. Cochrane Database Syst Rev 2022; (3): CD013520. [PMC free article: PMC8892837] [PubMed: 35238405]

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