The opacity of the maxillary sinuses on X-ray film in Waters' view in patients with nasal allergy was evaluated by a microdensitometer. The patients with nasal allergy were diagnosed with the positive results of the followings ; 1) eosinophilia in nasal secretion, 2) nasal provocation test, 3) intradermal skin test or radioallergosorbent test (RAST). The ratio of density of the maxillary sinuses and orbits was determined by a microdensitometer, and the ratio of the average degree of the opacity of the maxillary sinus to that of the ipsilateral orbit was designated as the M/O ratio. The normal range of the M/O ratio was set over the mean value - 2 standard deviations in the normal group. The results are followings.
1) The abnormal shadows in the maxillary sinuses were found out to be 36.9% in patients with nasal allergy.
2) Patients under 15 years-old had significantly higher incidence of abnormal shadows, especially in the bilateral sinuses compared with patients over 15 years old.
3) Polyps in the maxillary sinus were recognized in 5.0% of all the sinuses.
4) There were no significant differences for the incidence of abnormal shadow among the patients with nasal allergy caused by different antigens.