What causes conjunctivitis?
-
Infection is the most common cause.
-
Allergy is another common cause. For example, many people with hay fever (allergic to pollen) have red and inflamed conjunctiva.
-
Irritant conjunctivitis sometimes occurs. For example, your conjunctiva may become inflamed after getting some shampoo in your eyes. The chlorine in swimming baths is a common cause of mild irritant conjunctivitis.
The rest of this leaflet is about conjunctivitis caused by infection.
Types of infective conjunctivitis
Common infective conjunctivitis
Most cases of infective conjunctivitis are caused by common bacteria and viruses - often the same ones that cause coughs and colds. Conjunctivitis commonly develops when you have a cold or cough. Sometimes it occurs alone. In the vast majority of cases, infective conjunctivitis is not serious and clears within a week or so without leaving any permanent damage to the eye.
More serious types of infective conjunctivitis
Rarely, infective conjunctivitis is more serious. For example:
- Conjunctivitis may develop in addition to keratitis (infection of the cornea). This is most commonly due to an infection with the herpes virus (the cold sore virus). If you have keratitis you are likely to get eye pain rather than just surface irritation, and often blurring of vision.
- A virus called adenovirus can sometimes cause a serious and prolonged conjunctivitis.
- Conjunctivitis in newborn babies can be caused by germs called chlamydia or gonorrhoea. These are serious sexually transmitted infections and need urgent treatment if they affect the eye of babies. (If a mother has one of these infections in her vagina, they can be passed onto the eye of their baby during childbirth.) Note: this is different to the very common 'sticky eye' of newborn babies caused by a blocked tear duct. A blocked tear duct with sticky eye does not cause redness and inflammation of the conjunctiva. See separate leaflet called 'Blocked Tear Ducts of Babies' for details.
- Some adults develop conjunctivitis due to chlamydia.
- When conjunctivitis is just part of a more serious infection of deeper structures of the eye which may be indicated by eye pain, reduced vision, or swelling around the eye.
What are the symptoms of common infective conjunctivitis?
- One eye may be infected, but it usually spreads to both eyes. The 'whites' of the eyes look inflamed, and red or pink.
- The eyes may feel gritty and may 'water' more than usual.
- Some mild soreness may develop, but it is not usually very painful.
- The eyelids may become swollen, and are often stuck together with gluey material ('discharge') after a sleep.
- Vision is not normally affected. You may get some blurring of vision due to discharge at the front of the eye. However, this clears with blinking.
What is the treatment for common infective conjunctivitis?
-
Not treating is a common option for mild or moderate infections. The tears contain chemicals that fight off bacteria. Without treatment most cases of infective conjunctivitis clear on their own within 1-2 weeks, and often within 2-5 days. If symptoms get worse then see a doctor to check your eye and to see if you need treatment.
-
Bathing the eyes with cool clean water may be soothing.
-
Lubricant eye drops may reduce eye discomfort. These are available over the counter, as well as on prescription.
-
An antibiotic eye drop or ointment may be prescribed in some cases. This tends to be for more severe cases, or for those that do not clear on their own. (Tell your doctor if you are pregnant as some eye drops may not be suitable.)
Other general advice
- Do not wear contact lenses until symptoms have completely gone, and for 24 hours after the last dose of any eye drops or ointment.
- You can clean away secretions from eyelids and lashes with cotton wool soaked in water.
- Infective conjunctivitis is contagious. The likelihood of passing it on is not high unless you are in close contact with others. However, until the infection has gone, to help to prevent passing it on:
- Wash your hands regularly, particularly after touching your eyes.
- Do not share towels, pillows or utensils.
What should I look out for?
-
Serious infections. Most conjunctival infections are not serious, do not harm the eye, and clear in a few days. However, some infections such as herpes or chlamydia persist longer than usual, are more serious, and need special treatment. These may start off like a common conjunctivitis but become worse.
-
Other eye problems. Sometimes it is difficult for a doctor to tell the difference between infective and allergic conjunctivitis. They can appear very similar. This is often a problem in the hay fever season when red, watery eyes are common. Also, some other eye conditions can cause a red eye and may be mistaken at first for conjunctivitis.
Therefore, see a doctor if symptoms change, or do not settle within a few days, or if you are concerned that you have anything other than a common conjunctivitis. In particular, see a doctor urgently if:
- You develop marked eye pain.
- Light starts to hurt your eyes (photophobia).
- Spots or blisters develop on the skin next to the eye.
- Your vision becomes affected.
- Your newborn baby develops conjunctivitis.
Does a child with conjunctivitis need to stay off school?
Guidance from the Health Protection Agency states that it is not necessary to exclude a child from school or childcare if they have infective conjunctivitis, unless there is an outbreak of several cases. If an outbreak occurs, advice should be sought from the Health Protection Agency or other health professional by the school or childcare centre.
References
-
Conjunctivitis - infective, Clinical Knowledge Summaries (2007).
-
Sheikh A, Hurwitz B.; Antibiotics versus placebo for acute bacterial conjunctivitis. Cochrane Database of Systematic Reviews 2006, Issue 2. Art. No.: CD001211.
-
HPA; Guidance on Infection Control In Schools and other Child Care Settings. Health Protection Agency (December 2006).
© EMIS and PiP 2008 Updated: 13 May 2008
