Conjunctivitis: Causes of Pink Eye
Conjunctivitis is most commonly caused by the same virus that causes the runny nose and sore throat of the common cold.
Bacterial infections cause conjunctivitis that produces lots of sticky pus in the eye. Some bacterial infections, however, may cause little or no discharge. Sometimes the bacteria that cause pink eye are the same that cause strep throat. Both bacterial and viral conjunctivitis are easily spread from person to person.
Sometimes having an allergic reaction to pollen or animals can cause conjunctivitis. So can irritation from cigarette smoke, car fumes, pool chlorine or other toxic substances. The main symptom of allergic pink eye is itchy eyes. Other symptoms include red, burning and tearing eyes and puffy eyelids. Allergic conjunctivitis is not contagious.