Bacterial infections can cause a red eye which is associated with a pus or discharge from the eye, or they can cause a red eye which is associated with crusting of the eyelashes with little or no discharge. Viruses can cause conjunctivitis, such as the familiar red eyes, sore throat, and runny nose of a common cold. Viral conjunctivitis usually produces a watery discharge and lasts from one to two weeks. Cloth handkerchiefs and towels should not be shared during this time. Handwashing will also help prevent the spread of this infection.
Allergies can also cause a conjunctivitis which produces a discharge.
Allergies, like hay fever, can make the eyes itchy. Other allergies may only produce a chronic red eye. Environmental irritants such as smoke or fumes may cause conjunctivitis. Any type of conjunctivitis is aggravated by dryness of the eyes. The symptoms described above may not necessarily mean that you have conjunctivitis.