['Persistent allergic rhinitis (PER) has a moderate impact on the sense of smell, but no controlled study has reported the effect of antihistamines on the loss of smell in patients with PER.', 'Patients with PER and subjective loss of the sense of smell (n = 27) were included in this pilot randomised, double-blind, placebo-controlled study. Nasal symptoms, nasal endoscopy, skin prick test, acoustic rhinometry, peak nasal inspiratory flow, nasal nitric oxide (nNO), and olfactometry (Barcelona Smell Test-24; BAST-24) were performed and evaluated in all PER patients at baseline and after 7 and 30 days of treatment with levocetirizine 5 mg or placebo.', 'The study population was randomized into two homogeneous groups: levocetirizine (n = 14) and placebo groups (n = 13). The evolution of symptoms reflected the therapeutic effect of levocetirizine treatment on rhinorrhea, nasal itching, eye itching, sneezing, and the total symptoms score after 7 and 30 days. Significant improvement in loss of smell by a visual analog scale (VAS) was observed after 7 days of levocetirizine treatment (7.2 ± 4.3; p < 0.05) compared to placebo (-9.4 ± 6.2). Improvement in smell identification by BAST-24 was strongly correlated (r = 0.72; p < 0.05) with smell improvement by VAS after 30 days. After 7 days of treatment with levocetirizine, the nNO values decreased (-494 ± 188) compared to placebo (155 ± 284 ppb; p < 0.05).'] Is the loss of smell in persistent allergic rhinitis improved by levocetirizine due to reduction of nasal inflammation but not nasal congestion ( the CIRANO study )?