Red eye is a common problem that can affect one or both eyes. The redness associated with red eye comes from blood vessels on the surface of your eye that are expanded (dilated) due to some form of irritation or infection.
Call 911 or your local emergency number for red eye if:
Occasional, brief periods of red eye are usually no cause for worry. If you think the redness is caused by a reaction to over-the-counter eyedrops, try a different brand or take a break from using them.
Contact your doctor for an appointment if you have red eye that doesn't clear up after several days, especially if you have a thick or nearly continuous pus or mucous discharge.
Contact your eye surgeon if you're experiencing eye redness with pain and you've had eye surgery in the past or if you've recently had eye surgery or an eye injection.