Conjunctivitis is an eye condition where the conjunctiva (the clear membrane that covers the white part of the eye and lines the inner surface of the eyelids) becomes inflamed. The inflammation can have many causes—the most common are infection, allergy and irritation: Infectious conjunctivitis can be caused by bacteria or viruses. Bacterial conjunctivitis may start in one eye, but almost always involves both eyes. There is likely to be a gritty feeling and pus. Viral conjunctivitis may involve one or both eyes, making them red, itchy and watery. Allergic conjunctivitis is more common in people with allergic conditions, such as hay fever. It usually affects both eyes, and there are often other symptoms of allergies, such as an itchy nose, sneezing, and itchy and runny eyes. Irritant conjunctivitis can be caused by chemicals such as chlorine or chemicals in soaps, or air pollutants such as smoke and fumes. The different types of conjunctivitis can have different symptoms, and symptoms vary in different people. One of the most common symptoms is discomfort or pain in the eye, which may feel gritty. Many people have red eyes and swollen eyelids, and can be sensitive to bright lights. There may also be a discharge from the eye. In bacterial conjunctivitis, the discharge will be thick and coloured white, yellow or green; this may cause the eyelids to stick together when the person wakes in the morning. In viral or allergic conjunctivitis, the discharge may be thinner and clear.
How does it spread?
Viral and bacterial conjunctivitis can be spread by direct contact with eye secretions, or by contact with towels, washcloths, tissues and so on that have been contaminated with eye secretions. It can sometimes be spread by insects such as flies, when they fly from an infected person’s eye to another person’s eye.
The incubation period is usually 1–3 days.
Viral and bacterial conjunctivitis are infectious while there is discharge from the eye. Conjunctivitis caused by chemicals or allergies is not infectious.
Children with infectious conjunctivitis should be excluded until the discharge from the eyes has stopped.