The aim of this prospective study is to compare the prevalence of atopy in patients afflicted by nasal polyps with the atopy prevalence in healthy volunteers without nasal polyps, since systemic allergy and allergy in the nasal mucosa are still being debated as underlying causes for nasal polyps. Thirty-four cases with nasal polyposis without asthma and history of allergy or atopic disease were enrolled in the study and compared with 20 healthy volunteer controls in respect to asymptomatic food hypersensitivity. Hypersensitivity for 48 kinds of commonly consumed food in Turkey was investigated by an epicutaneuos, prick test, Multi-Test(R) 11 (Lincoln Diagnostic, Inc, USA), using a special applicator. The food allergy test was positive in 25 out of the 34 cases with nasal polyps and in 6 out of the 20 controls. The difference between the two groups was statistically significant (chi(2) = 0.000, P < 0.001). The number of skin tests with positive results In patients with nasal polyps ranged from I to 37 (mean +/- S.D. = 10.0 +/- 7.9), whereas in the control subjects the range was I to 10 (mean S.D. = 4.0 +/- 3.3). The difference in the number of food reactions was also statistically significant. Asymptomatic food hypersensitivity, being immunologically mediated, may be a triggering factor for the pathogenesis of nasal polyps. Therefore, treatment of asymptomatic food allergy in patients with nasal polyps may alleviate symptoms, slow the progress of nasal polyps and prolong the disease-free interval after polypectomy.