The late asthmatic reaction is in part independent from the early asthmatic reactions

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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 much more severe, and the current knowledge believes that the EAR always precedes the LAR. In 20 patients with asthma and HDM allergy, a bronchial allergen provocation (BAP) was performed three times (BAP1–3) with a tapered allergen dose. Compared to BAP1, at BAP2 there was a significant decrease in the EAR from mean 39,25+13,37% to mean 33,55+5,25% (p<0,01), whereas the LAR remained unchanged: mean 28,10+10,95% to mean 30,31+7,77% (n.s). Only for BAP3 both the EAR and the LAR was significantly weaker than for the first two BAPs. The independence of the LAR from the EAR was further elucidated: At BAP3 in 3 (15%) patients, even the tapered allergen dose induced a dual asthmatic reaction. In 10 (50%) patients the allergen dose was too low to trigger a significant EAR and LAR. In 7 (35%) patients, there was no EAR but a significant LAR (Mean Max Fall FEV1 20.5+4.7%) recorded. Before and 24 hours, exhaled NO (eNO), eosinophils and distinct miRNAs were measured as markers of bronchial inflammation. Significant correlations (p<0.05) were found between the miRNAs (miR-15a-5p, miR-15b-5p and miR-374-5) the eNO as well as the decline in lung function 24 hours after BAP and The LAR (p<0.01). We can demonstrate that a LAR is induced in some patients without an EAR to low allergen exposure. This leads to a strong inflammatory reaction with an increase in eNO and a decrease in FEV1 after 24 hours. Accordingly, these individuals are at greater risk of asthmatic symptoms and remodelling with loss of lung function than patients who do not have a LAR. Publication History Article published online: 28 February 2025 © 2025. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany

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