Conjunctivitis: Do antibiotics make a difference?

In more than half of all people who have conjunctivitis that is caused by bacteria, the infection goes away without treatment within two to five days. Antibiotic eye drops or ointment can speed up recovery, though. Adverse effects are rare.

Conjunctivitis makes people’s eyes red and inflamed. It often affects both eyes because the infection can spread from one eye to the other. Your eyes get watery and produce a sticky, yellowish-white discharge that makes your eyelids stick together. They may be sore too. The infection usually gets better without any treatment within two to five days.

Conjunctivitis is generally harmless. In people who wear contact lenses, however, the infection can spread to the cornea (the clear surface of the eye itself). This complication, also known as keratitis, is not common though: it is estimated that conjunctivitis leads to keratitis in about 3 out of every 10,000 contact lens wearers, but this is not certain.

If conjunctivitis is caused by bacteria or viruses, it is contagious and can spread to other people, or spread from one eye to the other and then back again, re-infecting the first eye. Conjunctivitis that is caused by viruses is much more contagious than conjunctivitis that is caused by bacteria. Antibiotics only work against bacteria, and not against viruses. Because conjunctivitis usually goes away so quickly, though, it is generally not worth doing tests to find out if it is a bacterial or viral infection. If someone has conjunctivitis, doctors often presume that bacteria are involved and then prescribe antibiotics in the form of eye drops or ointments. Sometimes conjunctivitis is linked to an allergy. Then it is treated with allergy medicines like antihistamines.

Treatments for conjunctivitis

When someone has conjunctivitis there is often no need to do anything other than wait and relieve the symptoms with simple strategies. Some people use non-antibiotic eye drops, and the use of cold or lukewarm eye pads is common too. These can be made by, for example, soaking a cloth in cold camomile tea or in water that has been boiled. However, there is not enough research on these approaches to be able to say whether they have a benefit, no effect, or are even harmful. Some people have an allergic reaction to camomile. And a moist cloth may even make the infection worse.

Another common treatment for conjunctivitis is antibiotics, applied several times a day in the form of eye drops or ointments.

Research on antibiotics in the treatment of conjunctivitis

To find out whether antibiotics have an extra benefit in the treatment of ordinary conjunctivitis, researchers from the Cochrane Collaboration looked for clinical trials that compared ointments or eye drops (with and without antibiotics) with each other. They were only interested in trials in which the participants were randomly assigned to one of the treatment groups (so-called randomized controlled trials). You can read more about that kind of research here.

They found five of these trials involving a total of just over 1,000 people with conjunctivitis. The participants were children and adults with conjunctivitis that had lasted for less than four weeks.

Antibiotics can speed up recovery

65 out of 100 people who did not use antibiotics recovered within two to five days (65%), compared to 79 out of 100 people who used antibiotics (79%). In other words, taking antibiotics helped clear up the infection faster in about 14 out of every 100 people (14%). This benefit was still noticeable for up to ten days after treatment.

None of the trials reported that antibiotics had adverse effects or that the conjunctivitis spread to the cornea. This suggests that conjunctivitis does not often lead to keratitis. The trials also did not provide enough information to be able to draw any conclusions about whether antibiotics helped prevent the infection spreading, either between the person’s eyes or to other people.

Conjunctivitis can be contagious and hard to get rid of, particularly if it is caused by viruses. But there are several things that can be done to try to stop viral infections from spreading. Viruses are easily spread when people use the same towels and washcloths, for example. The germs are also very likely to be spread by touching the eye with your fingers, so washing your hands after doing so could help keep a viral infection under control. Better still: avoid touching your eyes with your hands altogether. Another important way to protect others from infection is by not shaking hands with them and not touching their face until your conjunctivitis has cleared up.

Author: German Institute for Quality and Efficiency in Health Care (IQWiG)

© IQWiG (Institute for Quality and Efficiency in Health Care)