Outside the neonatal period, a Gram stain is usually not needed unless the conjunctivitis lasts longer than 7 days. The presence of vesicles or superficial corneal ulcerations suggests herpetic keratoconjunctivitis. Differential diagnosis of conjunctivitis Systemic diseases. Allergic conjunctivitis Allergic eye disease is characterized by pronounced ocular itching, redness, tearing, and photophobia. This recurrent disease has seasonal exacerbations in the spring, summer, and fall.
Allergic conjunctivitis is characterized by mild swelling and injection of the conjunctiva.