Conjunctivitis is inflammation (swelling) of the conjunctiva. The conjunctiva is the transparent membrane (thin layer of cells) that covers the white part of the eyeball and the inner surfaces of the eyelids.
There are three types of conjunctivitis, each with a different cause. These are:
* irritant conjunctivitis
* allergic conjunctivitis
* infective conjunctivitis
Irritant conjunctivitis occurs when an irritant, such as chlorine (a chemical often used to purify water) or an eyelash, gets into the eyes, making them sore. Do not rub the eyes as this can make the condition worse. The conjunctivitis should settle once the irritant is removed. If the eyes are very red and painful, seek medical attention immediately.
Allergic conjunctivitis occurs when the eyes come into contact with an allergen. An allergen is a substance that makes the immune system (the body’s defence system) react abnormally, causing irritation and inflammation. For more information on this type of conjunctivitis, see allergic conjunctivitis.
Infective conjunctivitis is caused by a virus, bacteria or a sexually transmitted infection (STI), such as chlamydia or gonorrhoea. The most common symptoms include:
* reddening and watering of the eyes
* a sticky coating on the eyelashes, particularly when waking up in the morning
How common is infective conjunctivitis?
Infective conjunctivitis is very common and is responsible for 35% of all eye-related problems recorded in GP surgeries. There are 13-14 cases for every 1,000 people every year.
Infective conjunctivitis is most common in children and the elderly. This may be because children come into contact with more infections at school. Elderly people may be more prone to infections as their immune system (the body’s defence system) may be weaker.
Infective conjunctivitis rarely requires medical treatment. If the infection is not caused by an STI, it will normally heal by itself within one or two weeks.
If the infective conjunctivitis is caused by an STI, the condition may last several months, rather than weeks. The STI may also require separate treatment.
For most people, the condition does not cause any complications. However, newborn babies (up to 28 days old) are at risk of a more serious infection. In severe cases, this could permanently damage the eyes.
* show glossary terms
An allergen is a substance that reacts with the body’s immune system and causes an allergic reaction.
The immune system is the body’s defence system, which helps protect it from disease, bacteria and viruses.
Inflammation is the body’s response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.
Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and others are good for you.