What Are the Causes and Risk Factors of Conjunctivitis?

Although general population consider that the condition of conjunctivitis is always contagious, but it is not true. Not always conjunctivitis is infectious, but non-infectious conjunctivitis does occur. The ratio of occurrence though largely varies between infectious and non-infectious conditions – 70% contagious and 30% non-contagious on average.

Contagious conjunctivitis is caused by either bacteria or virus. Bacteria like pneumococci, staphylococci, chlamydia trachomatis or streptococci can cause contagious conjunctivitis. Bacterial conjunctivitis occurs in 50% of the cases and viral conjunctivitis occurs in 20% of the cases.

Non-contagious conjunctivitis accounts for 30% of the cases and it occurs due to allergic reactions like grass or pollen, chemicals such as smoke, domestic cleaners or air pollutants or causal disorders like cytomegalovirus (CMV), Crohn’s disease, rheumatoid arthritis, ulcerative colitis, Kawasaki’s disease or lupus.

Moreover, conjunctivitis occurs as a result of traumatic hemorrhage or subconjunctival hemorrhage. A moderately unbolted tear duct may also result in developing conjunctivitis. In addition, herpetic conditions such as herpes zoster or herpes simplex can also result in developing conjunctivitis.