House dust mites (HDM) are the world's most important cause of allergic asthma. It is unclear why some patients with HDM allergy develop an early asthmatic reaction (EAR) only, whereas others react with a dual asthmatic reaction-EAR plus late asthmatic reaction (LAR). In patients with LAR, the symptoms and bronchial inflammation are more severe, and the current knowledge suggests that the EAR always precedes the LAR. The aim of the present study was to investigate whether a LAR can occur separately even without a significant EAR. In a pilot study of 20 patients with asthma and HDM allergy, a bronchial allergen challenge (BAC) was performed on three separate occasions with a tapered allergen dose. Before and 24 h later, exhaled NO (eNO), eosinophils and miRNAs were measured as markers of bronchial inflammation. Compared to BAC1, at BAC2 there was a significant decrease in the EAR from mean 39.25 ± 13.37% to mean 33.55 ± 5.25% (