The symptoms of conjunctivitis will depend on what's causing the condition.
However, the two main symptoms are usually:
- eye redness – as a result of the inflammation and widening of the tiny blood vessels in the conjunctiva (the thin layer of cells covering the front of the eyes)
- a discharge – the conjunctiva contains thousands of cells that produce mucus and tiny glands that produce tears – inflammation causes the glands to become overactive, so that they produce more water and mucus
Only one eye tends to be affected at first, but symptoms usually affect both eyes within a few hours.
If you have infective conjunctivitis, you may also have:
- a burning sensation in your eyes
- a feeling of grit in your eyes
- a sticky coating on the eyelashes – usually when you first wake up in the morning
- an enlarged lymph node (gland) in front of the ear
You may have itchy eyes if you have allergic conjunctivitis.
The pattern of symptoms for allergic conjunctivitis depends on the substance you're allergic to.
Allergies to pollen (hay fever) occur during certain parts of the year. You can have an allergy to:
- tree pollen, released during spring
- grass pollen, released during the end of spring and beginning of summer
- weed pollen, released any time from early spring to late autumn
It's highly likely that the pollen will also cause other symptoms, such as sneezing and a runny or blocked nose.
Allergies to dust mites or animal fur cause symptoms throughout the year. Both eyes are usually affected and you may find the symptoms worse in the morning.
Some people develop an allergy to eye drops. This is known as contact dermatoconjunctivitis and it can also affect your eyelids, causing them to become dry and sore.
Some people are allergic to wearing contact lenses, which is known as giant papillary conjunctivitis. The symptoms progress much more slowly and you may also develop small spots on the inside of your upper eyelids. This type of conjunctivitis carries a high risk of complications, so you need to seek medical advice as soon as possible
When to seek medical advice
Most cases of conjunctivitis aren't a cause for concern, but you should contact your GP if you think you have it, particularly if you think it's related to wearing contact lenses.
Your GP can check whether there's a more serious underlying cause of your symptoms.
When to seek immediate medical advice
The following symptoms could be the sign of a more serious eye condition:
- pain in your eyes
- sensitivity to light (photophobia)
- disturbed vision
- intense redness in one eye or both eyes
Contact your GP immediately if you experience any of these symptoms. If this isn't possible, visit your nearest accident and emergency (A&E) department.