What causes conjunctivitis?

Many different sources of eye irritation can cause conjunctivitis.  The most common are infections, allergies, and environmental irritants.  Infectious causes of conjunctivitis include bacteria and viruses. Both of these can be quite contagious, so contact with the patient’s tears should be avoided.  Wash your hands frequently, and avoid touching or rubbing your eyes. Don’t share washcloths, towels or pillowcases with anyone else.  Don’t share eye drops or cosmetics such as eyeliner, eye shadow or mascara.  Replace them after you’re healed to avoid re-infection. Your eye doctor may recommend that you discontinue contact lens wear if you are diagnosed with conjunctivitis or replace your contact lenses after you’re healed.  See your ophthalmologist if conjunctivitis is suspected.