Most forms of follicular conjunctivitis are a local host response to an exogenous substance or agent producing prominent subconjunctival lymphoid follicles. Viruses, chlamydia, and bacteria can produce the problem. Careful history, clinical examination, and simple lab tests are required to ferret out specific causes. Symptoms and signs depend on the causative agent but may include watery discharge, conjunctival hyperemia, sandy/gravely feeling, blurry vision, and photophobia. There are both acute and chronic forms of follicular conjunctivitis with the latter defined as those cases of follicular conjunctivitis that persist for more than 16 days. In the acute form, presentation is often unilateral followed within a week by involvement of the second eye. Frequently in the acute form, preauricular lymphadenopathy on the affected side is present.

Note that conjunctival follicles do not occur in neonates, yet they are susceptible to many of the same diseases that cause them in adults.