In mid-May 1988 ocular troubles occurred in many children in several schools. We suspected them to be victims of a mass outbreak of allergic conjunctivitis induced by grass pollen from clinical and epidemiological observation. We have investigated the matter and taken measures to solve the problem.
The schools in which ocular troubles occurred are in an urbanized rural region in Kanagawa Prefecture. An on-the-spot study found the schools are surrounded by rice fields. When the troubles occurred in May the grass for cattle grew densely on the fields and was just in full bloom. This grass, known as Italian ryegrass (Lolium multiflorum), was planted eleven dairy farmers who borrowed the fields.
Some data were collected from the health records in the schools. And some were collected by the questionnaires taken when children came to the nurse's office of the school to treat their conjunctivitis. It was irevealed that similar troubles had occurred around mid-May every year. In other seasons, the incident of conjunctivitis is sporadic. More than 100 children suffer from acute allergic symptoms every year. Inflammation manifests itself from late morning to early afternoon in windy warm days in mid-May and about half of the cases occur when they were outdoors. Symptoms of which children most frequently complained were eye itching and hyperemia in the conjunctiva. Other symptoms include tearing, nasal discharge, eye pain and swelling. Over 50% of the children suffered from them. In serious cases sclera was swollen forward as compared with cornea and looked like geratin. A sticky discharge was found in about 20% of the patients.