Health Conditions

What causes it?

Conjunctivitis may result from allergic, bacterial, and viral irritants; however, viral causes tend to be the most common cause of conjunctivitis.

Seasonal allergic conjunctivitis usually stems from an air-born irritant such as ragweed, pollen, or mold. When the conjunctiva is exposed to the irritant, a chain of events leads to the swelling, itching, and redness often associated with this form of conjunctivitis. First, the irritant is detected and marked by the body's immune system as foreign and unlike other cells. Then the target is marked for elimination. Combatant cells, called mast cells, arrive on the scene to remove the foreign attacker and cause the release of various inflammatory substances such as histamines. Histamines cause the uncomfortable symptoms associated with allergic conjunctivitis such as red, watery, itchy eyes.

A similar chain of events occur when the conjunctiva is exposed to bacterial or viral irritants. Bacterial and viral conjunctivitis are usually associated with a cold and both usually produce a discharge from the eye. Bacterial and viral conjunctivitis can be extremely contagious, and treatment should be sought immediately to prevent the spread to others.