Red eyes can be caused by a variety of factors, including dirty contact lenses, cigarette smoke, allergies, infections, dry eye, inflammation and glaucoma. Some of these problems are minor and readily treatable; others are medical emergencies. A sudden redness, especially accompanied by sharp pain, suggests the need for immediate medical care.
It is not necessarily recommended to use over-the-counter eye drops designed to relieve redness. These will constrict the blood vessels and reduce redness temporarily, but the blood vessels will dilate after the effect of the drops wears off. If used chronically, these drops may cause more of a “rebound” redness because of the constant constricting and dilating of the vessels.
Artificial tears, which simply lubricate the eye, are a better treatment for redness caused by irritants like pollution, cigarette smoke or nearby fires.
People who don’t adequately clean their contacts may get away with it for a while, but as you age, it could lead to chronic redness and irritation. Redness may also indicate that a contact lens doesn’t fit properly; it’s important to replace it with one that fits, since an ill-fitting lens may damage the eye.
Symptoms may also be a clue to the cause of eye redness. Itchy eyes may indicate an allergic response, tearing could be a sign of dry eye, and yellowish discharge may indicate an infection. The cause will determine whether chronically red eyes can be successfully treated. A comprehensive eye exam would be the main thing to do, to root out the cause.