Background. Allergic rhinitis (AR) significantly impairs the quality of life of the patients; however, a questionnaire alone is an insufficient and subjective measure of this condition. Obtaining an objective clinical assessment of the level of impairment will be valuable for its treatment. β-Endorphin is one of the most important mediators of both mental state and specific immunity. Thus, we investigated the possibility of using β-endorphin as a biomarker for evaluating the impairment level in AR. Methods. This study included 48 patients with AR and 32 healthy volunteers. The serum β-endorphin level was determined by enzyme immunoassay, and the serum-specific IgE and total IgE levels were determined by immunoblot assay. The Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) was used to assess the impairment level in the symptom duration. Results. The β-endorphin concentration was significantly decreased in AR patients compared to the healthy controls (p=0.000, p<0.05). There was significant negative correlation between the impairment level and serum β-endorphin level (correlation coefficient: -0.468; p=0.001; p<0.05), but there was no association between the serum β-endorphin and total IgE levels (p=0.947, p>0.05). Conclusion. β-Endorphin is a systemic biomarker that has the potential to assess the impairment level in AR and may therefore be a novel therapeutic target for the treatment of AR.