BACKGROUND: Nasal polyp (NP) is the most common mass lesion in the nose with unclear etiology and pathogenesis. OBJECTIVE: To investigate the association of allergy and type of cellular inflammation in Asian patients with NPs. METHODS: Immunohistochemical staining with a panel of antibodies for CD4+ and CD8+ T cells, B cells, Langerhans' cells, eosinophils, neutrophils, and mast cells were performed in pairs of NP tissue and middle turbinate (MT) biopsies from the same side of 48 patients and MT of controls. Serum total IgE and specific IgE to a panel of common local allergens were tested by the UniCAP (Pharmacia & Upjohn AB, Uppsala, Sweden) system. RESULTS: Atopy was found in 29.7% of NP patients. Strong correlations of cell scores were evidenced between the paired samples from nasal polyp patients. The cell patterns in nasal polyp mainly showed a combined cell infiltration with significantly higher CD8+ T cell, eosinophil and neutrophil scores, and an inverse median ratio of CD4+/CD8+ T cells as compared with the MT from controls. CONCLUSION: The similar immunohistochemical pattern of mucosal inflammation in NPs and the paired MT mucosa suggests a diffuse mucosal involvement. This indicates the necessity of anti-inflammatory treatment of changes in the adjacent nasal mucosa in addition to the surgical removal of NPs. Besides the well-recognized eosinophilic inflammation in Caucasian studies, predominant infiltration of T cells, especially CD8+ T cells, could be a key component underlying the pathogeneses of NPs.