(HealthDay News) -- Conjunctivitis occurs when the membrane that protects the eye, the conjunctiva, becomes inflamed. A red, watery eye is a primary symptom of this very contagious condition.

The University of Virginia Health System says possible causes of conjunctivitis include:

• An viral or bacterial infection.
• An allergic reaction, often to a seasonal allergen.
• Irritation from air pollutants or smoke.
• Irritation from soap, chlorine or cosmetics.
• Irritation from a chemical that makes contact with the eye.