Allergic conjunctivitis is swelling and redness of the membrane that lines the eye. It is caused by exposure to foreign matter. The affected part of the eye is called the conjunctiva. The conjunctiva is the mucous membrane layer that covers the white part of the eye.

What are the causes and risks of the condition?

Pollen is often the cause of the problem. Other vegetable proteins, animal proteins, dust and fungus spores can cause it, too. Sometimes the allergic reaction can happen within minutes. Other times the reaction can be delayed for hours or days. This problem seems to affect people who have other allergy problems. These include eczema, asthma, hay fever or hives.

Other common causes of allergic conjunctivitis are exposure to animal hair, such as cat hair, or feathers.

A less common form of allergic conjunctivitis comes from bacteria on the eyelid or skin. The cause is often the staphylococcus bacteria. This type of allergy may lead to styes, which are pimple-like infections of the glands in the eyelid. It may also cause chalazions, which are blockages of the oil glands in the eyelid. Long-term problems related to allergies in the eye rarely occur. However, if uncontrolled, the problem can spread to other parts of the eye, such as the cornea and the space between the cornea and the iris. This can cause inflammation of the iris, which is the colored part of the eye.