There are four main causes for red eyes, they are virues, bacteria, allerges ( such as pet dander and dust mited) and irritants such as smog or swimming pool chlorine that infect or irritate the eye and eyelid lining.The treatment for red eyes depends on the causes. It is not always necessary to see a eye doctor if your red eyes caused by viral conjunctivitis which will usually clear up in 7-14 days without treatment and without any long-term consequences. However, there are times when it is important to seek medical care, if your red eyes are accompanied by moderate to severe pain, intense redness in the eyes, vision problem such as sensitivity to light or blurred vision, and occurs in a patient who is immunocompromised from HIV infection, cancer treatment, or other medical conditions or treatments, or become worse or persist when a patient is suspected of having a severe form of viral conjunctivitis,bacterial conjunctivitis is being treated with antibiotics and does not begin to improve after 24 hours of treatment.