Causes may include any of the following: Viral conjunctivitis (most commonly adenovirus) Blepharitis Keratoconjunctivitis sicca Trachoma Chemical burns Ultraviolet (UV) light exposure (eg, welding arcs, sunlamps, snow glare) Contact lens overwear Systemic drugs (eg, adenine arabinoside) Topical drug or preservative toxicity Peripheral facial nerve palsy (including Bell palsy) Symptoms include photophobia, foreign body sensation, lacrimation, redness, and slightly decreased vision.