Currently, allergic rhinitis (AR) is the most common allergic disease worldwide. AR is defined as immunoglobulin E (IgE)-mediated chronic inflammatory disease of the upper airways. It characterizes by symptoms like nasal obstruction, rhinorrhea, nasal itching, and sneezing. The immune system and genetic susceptibility in the interaction with the environment lead to the development of AR. Many cytokines, chemokines and cells maintain allergic inflammation. Studies show that 10% to 30% of the adult population are affected, and that prevalence rates are increasing world widely. AR, nasal polyps (NP), as well as chronic rhinosinusitis (CRS) are all associated with eosinophilic infiltration and large quantities of mast cells (MCs) within the mucosa. The diagnosis and management of chronic sinonasal diseases involves the analysis of eosinophilic infiltration, MCs, and their markers eosinophilic cationic protein (ECP) and tryptase. Regarding nasal cancer, nasal allergies were found to exhibit a dual function: immune surveillance may help in the defense against malignant cells, but an opposite effect is observed in tissues with chronic stimulation and inflammation. In the present paper, we studied a group of 70 patients diagnosed with AR and NP, rhinosinusitis or nasal cancer, admitted to the Ear, Nose & Throat (ENT) Clinic of the Emergency City Hospital, Timişoara, Romania, between January 2016 and December 2020, and we identified 37 (53%) patients diagnosed with AR and NP, 25 (36%) patients diagnosed with AR and rhinosinusitis, and eight (11%) patients diagnosed with AR and nasal cancer. The average age of the patients was 53 years old. Every patient included in the study was histopathologically and immunohistochemically diagnosed.