The two main types of conjunctivitis are infective and allergic conjunctivitis. Irritant conjunctivitis is less common and is caused by getting something in your eyes, such as chlorine, an eyelash, make-up or touching your eyes after chopping chillies.
Infective conjunctivitis is contagious and caused by a bacteria or virus. This is the most common type and usually caused by the same bacteria or viruses as colds, coughs and flu. In adults, it is most commonly caused by a virus and in children it is more likely to be a bacterial infection. Between 33 and 78 per cent of cases result from a bacterial infection.
Common bacteria that cause conjunctivitis include Staphylococcus spp, Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. Sexually-transmitted infections (STIs) including chlamydia or gonorrhoea, are other less common causes.
Adenovirus which can result in a raised temperature and a sore throat, is a common cause of viral infective conjunctivitis.
Allergic conjunctivitis is usually caused by a reaction to pollen from grass or trees, dust mites or pet fur.
If you have infective conjunctivitis, first one eye and then both eyes are affected. The whites of your eyes will look red or pink and be inflamed. Eyes may be watery and feel 'gritty' and may be sore. Eyelids are often stuck together with sticky discharge when you wake up.
With allergic conjunctivitis, both eyes are affected. Your eyes will feel itchy, gritty and the skin inside your lids looks red and sore. Your eyes will be watery and eyelids can look puffy and swollen but there is no sticky discharge. You will normally have other allergic symptoms, such as sneezing and a blocked or runny nose.
Your GP or optometrist will examine your eyes to find out whether you have infective or allergic conjunctivitis, or if your symptoms could be caused by a more serious problem such as glaucoma, an STI (e.g. Chlamydia), uveitis (swelling of inner layer of your eye) or keratitis (a corneal infection, more common in contact lens wearers).
Your doctor may take a swab from your eye and send it off for testing if the cause is unclear or you haven't got better with treatment.
Who gets it?
Infective conjunctivitis is more common in children and the elderly, while allergic conjunctivitis affects those with allergic conditions such as hay fever or eczema.
You're more likely to develop infective conjunctivitis following a cold or cough. People with weakened immune systems, such as those with diabetes or taking corticosteroids, can be more prone.
If you suffer from blepharitis (a condition causing inflamed eyelids), this can make you more at risk of bacterial conjunctivitis.
Bacterial conjunctivitis usually clears up by itself within seven days without treatment, symptoms of viral conjunctivitis may take up to two weeks to go away. If it is severe, or lasts longer than this, treatment will depend on the type and cause.
For infective conjunctivitis that is severe or long-lasting, antibiotic eye drops can be prescribed or bought from a pharmacy without prescription. Chloramphenicol is the preferred choice and is effective against most strains of bacteria. If you can't use this or are pregnant, Fusidic acid drops are an alternative.
You can also buy simple lubricant eye drops from a pharmacy, which can relieve sore, sticky eyes.
Remove contact lenses until conjunctivitis has cleared and always replace with new ones after an infection. Infective conjunctivitis is very infectious; to avoid spreading it, wash your hands after applying eye drops or touching your eyes, don't share towels or make-up and wash towels and pillow cases frequently.
If conjunctivitis is caused by an allergy to pollen, dust mites or pets, you can buy antihistamine eye drops or mast cell stabiliser drops from a pharmacy to ease symptoms. These counteract the allergic reaction. Antihistamine drops (azelastine, emedastine, antazoline with xylometazoline) are used daily through the allergy season. Mast cell stabilisers (sodium chromoglicate, lodoxamide, nedocromil sodium) are good for managing allergic conjunctivitis over a longer period. Some eye drops available on prescription combine antihistamines and mast cell stabilisers.
The herbal supplement gingko biloba may be a useful supplement for protecting eye health by increasing blood flow to the area.
Kelp extract is a rich source of iodine, which is beneficial for eye health and is available as a supplement.