Role of nasal allergy in chronic maxillary sinusitis--diagnostic value of nasal challenge with allergen. The role of nasal allergy in chronic maxillary sinusitis without an air-fluid level was studied in 37 patients. Seventy-three nasal provocation tests with various inhalant allergens were performed in 37 patients by means of rhinomanometry, and maxillary sinus radiographs were performed before and repeatedly after the allergen challenge. Forty-one positive nasal responses (NRs) occurred in 29 patients; 13 were immediate only, 18 were late only, and 10 NRs were dual responses. Of these responses, 32 demonstrated radiographic changes, primarily an increase in mucosal edema and/or opacification. These responses were accompanied by increased pressure in the maxillary sinuses, acute headache, and sometimes otalgia. Eight patients did not develop any NRs; however, increased thickening of the mucosal membrane of the maxillary sinuses, accompanied by subjective symptoms, was recorded in three of these nonresponders. These results demonstrate the role of nasal allergy in some patients with chronic maxillary sinusitis, which may affect the diagnostic and therapeutic approaches to this disorder. 