Serum interleukin-17 levels are related to clinical severity in allergic rhinitis.

T helper (Th)-17 cells are a subset of T helper lymphocytes that exert regulatory activities. Recently, it has been reported that serum interleukin (IL)-17 levels are high in the most severe cases of birch allergy studied outside the pollen season.The aim of this study was to investigate a possible relationship between serum IL-17 levels and clinical parameters in patients with allergic rhinitis studied during the pollen season.In all, 56 patients with persistent pollen-induced allergic rhinitis were evaluated during the pollen season. Serum IL-17 levels were evaluated by enzyme-linked immunosorbent assay. Symptoms were assessed by visual analogue scale, drug use was monitored and peripheral eosinophils were counted.Serum IL-17 levels were significantly related to clinical symptoms, drug use and peripheral eosinophil counts (P = 0.0001 for all).This study provides evidence that serum IL-17 level assessment might be considered to classify allergy severity.