There is a thin layer of cells (membrane) between the inner surface of the eyelids and the whites of the eyes, called the conjunctiva.
Conjunctivitis is when the conjunctiva becomes inflamed. Another name for conjunctivitis is pink eye. Inflammation causes tiny blood vessels (capillaries) in the conjunctiva to become more prominent, giving the eye a red or pink look.
Types of conjunctivitis
There are three different types of conjunctivitis:
1) Irritant conjunctivitis
Something has irritated the area. It could be an eyelash that got stuck, or chlorine after a swimming in a pool. The eye(s) can become sore. People instinctively rub sore eyes, which unfortunately tends to irritate them more.
2) Allergic conjunctivitis
Allergic conjunctivitis happens when an allergen comes into contact with the eye, such as dust mites, pollen or animal fur. An allergen makes the body's immune system overreact, causing irritation and inflammation.
3) Infective conjunctivitis
Infective conjunctivitis is caused by a bacteria or virus
A viral or bacterial infection typically makes the eyes red/pink and watery. There will be sticky coating on the eyelashes. Infective conjunctivitis accounts for 35% of all eye-related problems recorded in GP surgeries by the National Health Service (NHS), UK. Children and elderly people tend to get it more than others.
The rest of this article focuses on infective conjunctivitis.
Symptoms of infective conjunctivitis
Typically one eye will be affected first, and a few days later the other one will too - although this is not always the case.
Signs and symptoms may include the following:
- The eye goes red - irritation and widening of the tiny blood vessels in the conjunctiva make the eye go red. If the eye becomes very red and painful you should see a doctor. If your vision is affected, or you develop photophobia (very sensitive to light) you should see a doctor too. Seeing the doctor if you have these symptoms is important because there is a chance that a more serious condition is causing them.
- Watery eye - there are thousands of cells in the conjunctiva that produce mucus, as well as very small glands that produce tears. When the area is irritated the tear glands become overactive, making the eye watery and shiny.
- Sticky coating on the eyelashes - this is most noticeable and annoying when waking up after a long sleep. Sometimes the eyelids are stuck together, as if by glue. The sticky coating is pus which is produced by the infection. Sometimes the coating can harden into a kind of crust. When this happens to a young child for the first time it can be very distressing - the parent or nearby adult needs to reassure the child that nothing bad has happened and that they will soon be able to open their eyes again after a "gentle wash".
- Sore eyes - some people describe the sensation as gritty, as if there were sand in the eyes.
- Swollen eyelids - the eyelids may swell when the conjunctiva becomes very inflamed, or if the sufferer has been rubbing them a lot.
- Swollen lymph node - the lymph node in front of the ear becomes swollen and slightly tender. The lymph node is part of the body's immune system, which fights infection. The lymph node may feel like a button under the skin.
- Respiratory tract infection - this may include flu-like symptoms, such as fever, headache, aching limbs, and sore throat.
On the next page we look at the causes of infective conjunctivitis and how it can be diagnosed. On the final page we discuss treatments for infective conjunctivitis and complications caused by the condition.