A marked increase has been noted recently in cases of nasal allergy in Japan. A solely rhinological approach to the mechanisms of nasal allergy onset is inadequate, however, since environmental factors are known to play an important role, in addition to a hereditary disposition for antibody production, which is believed to be the key factor behind the onset of nasal allergies. This study aims to determine which acquired factors play more important roles in producing these symptoms. This study sought to identify the characteristics of nasal allergy patients at the Jikei University School of Medicine Hospital, and the relationship between clinical findings and onset-modifying factors such as age, sex, and housing conditions. The objective was to elucidate the pathology of nasal allergies and why the allergies have become more prevalent. The results of this study can be summarized as follows. 1. Incidence of nasal allergies is clearly on the rise: In a 10-year period from about 1968-1969 to about 1979-1980, the ratio of nasal allergy cases to total new outpatient cases increased eight-fold. 2. The number of older patients making their first visit to the department of otorhinolaryngology for nasal allergy treatment has increased, indicating that the range of ages affected has widened. At the same time, age at onset clearly is falling, a fact which corresponds to the increasing number of pediatric allergy cases in primary care institutions. 3. The proportion of patients with histories of allergic disease remains about the same. So the number of genetically predisposed individuals is not believed to have increased suddenly. 4. The distribution of ages at onset was different for males and females. Male onset tended to occur during childhood, and female onset during early adulthood. But in both males and females, the clinically positive findings were more pronounced in children than in adults, proving that exacerbated organ sensitivity and immunological reactivity are important determinants of nasal allergy onset. It seems, therefore, that special predisposing factors other than immunological reactivity are part of a complex group of causes that determine the onset of female nasal allergy cases found more frequently in young adults than in children. 5. To determine the possible influence of microscopic environmental factors, I investigated the relationsphip between the incidence of nasal allergy vs. housing conditions: what kind of homes the patients lived in, whether they had moved or rebuilt their homes recently, etc. No significant correlation was observed in children between the incidence of house dust nasal allergy and the laboratory results to any above-mentioned environmental factor. In adults, however, there was a (P<0.01) disproportionately hight incidence of house dust allergies living in western-style homes. The house dust sensitivity rate revealed by tests was also isgnificantly greater (P<0.01) in patients living in western-style or poorly swept homes. Further study is required to determine whether these differences between children and adults are due to quantitative differences in antigen exposure, the extent of changes in the patints' living environment, or differences in some basic predisposing factor. The present clinical study shows clearly that nasal allergies take on different forms in a complex association of several onset-modifying factors, including predisposition, age, sex, and environmental factors.