1. Bacteria – when the eyes are red with yellow or green drainage oozing or crusting in the eye throughout the day and night, then bacteria are usually the culprit. The eyelids may also be swollen. Affects one or both eyes.
2. Virus – when the eyes are very red, but there is no drainage, or only a small amount of drainage or crusting upon waking up, then it is probably viral conjunctivitis. Usually affects both eyes
3. Allergy – allergic conjunctivitis is usually seasonal, mostly in the spring. The eyes are usually red with no drainage, and unusually itchy. Usually affects both eyes.
4. Foreign body – a piece of sand or dirt stuck under the eyelid can cause redness, tearing, pain and drainage. Usually affects one eye.
5. Plugged tear duct– this is a problem for newborns up to one year of age. It is eye drainage without any eye redness. Affects one or both eyes. Click on it for more info.
6. Scratched eye– can cause redness, tearing, and is very painful. Affects only one eye. Click on it for more info.
Bacterial and viral conjunctivitis are the only two causes that are contagious. They are spread by contact with the eye drainage or tears.
Pink eye is generally not serious and should improve with treatment or time. You should contact you doctor if: