A 4-year-old boy presented with a sudden swelling in his right eye associated with itch, unilateral tearing and presence of jelly-like oedema in the bulbar conjunctiva. The diagnosis was conjunctival chemosis. Conjunctival chemosis is the oedematous imbibition of the tissues underlying the bulbar conjunctiva that determines the jelly-like swelling from the eyeball. It is an unspecific sign of eye inflammation that in most cases is ascribable to allergic diathesis or viral or bacterial infections. The diagnosis is clinic and therapy should be targeted to the treatment of its trigger.