Conjunctivitis causes

Causes
Conjunctivitis is most commonly caused by viruses, often adenovirus, but many other factors can lead to its occurrence. Other causes include: Conjunctivitis is spread from person-to-person by: Newborns can be infected by bacteria in the birth canal. This condition is called ophthalmia neonatorum, and it must be treated immediately to preserve eyesight. Additionally, neonatal conjunctivitis is a red eye in a newborn caused by irritation, a blocked tear duct, or infection.
 * Allergies (allergic conjunctivitis)
 * Bacteria
 * Certain diseases
 * Chemical exposure
 * Chlamydia
 * Fungi
 * Parasites (rarely)
 * Use of contact lenses (especially extended-wear lenses)
 * Direct contact with the infected person’s eye drainage or drainage from the person’s cough, sneeze, or runny nose.
 * Indirect contact with objects that may have the infected person’s drainage on them (e.g. eye makeup applicators, towels, shared eye medications).
 * Contact with the infected person’s fingers or hands which may contain the virus or bacteria.