Background: The SQ House Dust Mite (HDM) SubLingual ImmunoTherapy (SLIT)-Tablet (Acarizax) is the only allergen immunotherapy authorized by European regulatory authorities to treat HDM-induced allergic asthma (AA) that is not wellcontrolled by inhaled corticosteroids and associated with mild-to-severe HDM allergic rhinitis (AR). The aim of this study was to add evidence on the safety of the SQ HDM SLIT-Tablet in patients with AR, alone or with AA, under real-life conditions. Methods: This was a French "real-life", multicenter, non-comparative, longitudinal, prospective study. It included patients initiating the SQ HDM SLIT-Tablet for either persistent moderate-to-severe HDM AR or AA not well-controlled by inhaled corticosteroids and associated with mild-to-severe HDM AR. Adverse Events (AEs) were collected at the first intake and throughout the study. Logistic regression was used to compare safety according to asthma control before treatment initiation.Results: Between May 09, 2018 and May 29, 2019, 1526 patients were enrolled at 185 sites and 1483 were included in the safety population (SAF). Of them, 33.6% had suspected clinical manifestations of AA. Asthma was uncontrolled for 18.2% of the patients, partially controlled for 27.9% and well-controlled for 53.8%. Overall, 31.9% of the SAF patients experienced at least one AE. The percentage of patients with AEs was 29.9% among patients with AR alone and 35.9% among those with AA (p = 0.0193). No significant difference was observed in the rate of AE or SAE depending on asthma control at inclusion (2.2% of SAEs reported for patients with uncontrolled asthma, 1.4% for partly controlled and 1.1% for well-controlled).Conclusions: The overall results indicate a good SQ HDM SLIT-Tablet safety profile consistent with that reported in previous studies, regardless of asthma control.