Conjunctivitis is an inflammation that occurs in the thin layer of structure on the surface of the white eyeball and the inner surface of the eyelid. Conjunctivitis can be caused by infections such as bacteria, viruses, chlamydia, fungi, parasites, etc., and by environmental factors like sand, smoke, ultraviolet exposure, and chemical injuries from acids, alkalis, or toxic gases. It can also be an inflammatory response of the conjunctiva due to allergic or systemic diseases including tuberculosis, syphilis, thyroid disorders, or surrounding tissues of the eye such as the cornea, sclera, eyelids, nasal cavity, and sinuses. Common symptoms of conjunctivitis include red eyes, a sensation of a foreign body in the eye, burning, itching, photophobia (sensitivity to light), tearing, and increased discharge. Sometimes it can also cause eye pain.