(HealthDay News) -- Conjunctivitis is an inflammation of the thin, transparent layer that lines the inner eyelid and covers the white part of the eye.

According to the American Optometric Association, the three main types of conjunctivitis are infectious, allergic and chemical.

The infectious type -- which is also the most common -- is called pink eye and is caused by a contagious virus or bacteria. Your body's allergies to pollen, cosmetics, animals or fabrics often bring on allergic conjunctivitis. Irritants such as air pollution may produce the chemical form.

Common symptoms of conjunctivitis are red watery eyes, inflamed inner eyelids, blurred vision, a scratchy feeling in the eyes and a discharge. Conjunctivitis can develop into something that can harm vision, so you should see your optometrist for diagnosis and treatment.

Infectious conjunctivitis caused by bacteria can be treated with antibiotic eye drops. Other forms, caused by viruses, can't be treated with antibiotics -- they must be fought off by your body's immune system.

To control the spread of infectious conjunctivitis, keep your hands away from your eyes, wash your hands before applying eye medications and do not share towels, washcloths, cosmetics or eye drops with others.