The white part of your eye and the inner surfaces of your eyelids are covered by a transparent membrane (thin layer of cells) known as the conjunctiva. If the conjunctiva becomes inflamed, you have a condition called conjunctivitis.
There are three types of conjunctivitis: irritant, infective and allergic. Each type of conjunctivitis is caused by different factors.
Irritant conjunctivitis
Irritant conjunctivitis occurs when an irritant such as chlorine or an eyelash gets into your eyes. This can make your eyes sore, and if you rub them it can make the soreness even worse. Avoiding the irritant and not rubbing your eyes will help. However, if your eyes are very red and painful, you should seek medical help immediately.
Infective conjunctivitis
Infective conjunctivitis is caused by a virus or bacteria.
Allergic conjunctivitis
Allergic conjunctivitis is a common condition and is responsible for 15% of all eye-related problems recorded in GP surgeries. It occurs when your eye comes into contact with an 'allergen'. An allergen is a particular substance that makes your body's immune system react abnormally, causing irritation and inflammation in the affected body part. This is known as an allergic reaction. Common examples of allergens include pollen, dust mites and animal fur.