Background: A perennial house dust mite-associated allergic rhinitis has a major impact on the quality of life of patients and is associated with a high socioeconomic burden. The most common symptoms of allergic rhinitis include a runny nose and nasal congestion, sneezing, itching of nose, mouth and/or throat, and/or ocular symptoms. Affected patients often develop allergic bronchial asthma. Therapy options for allergic rhinitis include allergen avoidance, symptomatic treatment, and allergen immunotherapy. Allergen immunotherapy is the only disease-modifying treatment that can permanently alleviate the symptoms of allergic rhinitis. In July 2021, a new sublingual mite tablet was approved in Germany. Methods: This review summarizes clinical studies on the 300 IR (index of reactivity) mite tablet in adolescents and adults with house dust mite-associated allergic rhinitis and presents the results. Results: In the phase II and phase III studies considered here, different dosages of the mite tablet were investigated. The 300 IR mite tablet showed the best benefit–risk profile and has been approved in Europe, Japan, South Korea, Australia, and New Zealand for the treatment of house dust mite-associated allergic rhinitis. Conclusion: Allergen immunotherapy with the 300 IR mite tablet is an effective treatment that relieves allergic symptoms, reduces the need for symptomatic medication, and improves the quality of life in both adults and adolescents with house dust mite-associated allergic rhinitis. At the same time, treatment with the 300 IR mite tablet is well tolerated. Mild to moderate reactions at the application site subside after a few days.