There are many causes of eye redness. The sudden onset of a red eye or red eyes can be frightening. In many
cases it is not a serious problem. For instance if you notice a bright red eye with no pain or discharge from
your eye it's probably a subconjunctival hemorrhage. Sneezing, coughing, or rubbing the eye can cause one of the
small vessels on the surface of the eye to bleed. This condition is not dangerous and resolves on its own.