Nasal obstruction is sustained by eosinophilic inflammation in allergic rhinitis. The decongestion test consists of spraying an intranasal vasoconstrictor drug to evaluate the reversibility of nasal airflow limitation. The aim of this study was to assess the relationships of both the number of nasal eosinophils and the degree of nasal obstruction symptom with the reversibility of nasal airflow after the decongestion test in patients with perennial allergic rhinitis (PAR). Eighty-three patients with PAR were studied. Total symptom score, sensitization, rhinomanometry, and the decongestion test were performed in all the patients. Using multivariate analysis, the eosinophils number was significantly (and inversely) associated (p < 0.001) with the reversibility of nasal airflow, whereas the nasal obstruction symptom degree was not (p = 0.338). This study provides evidence of a significant association between nasal eosinophils and the reversibility to the decongestion test in patients with PAR.