Allergen-specific immunotherapy (AIT) can alter the natural course of an allergic disease. It is widely held that the efficacy of a given therapeutic modality should be proven by well-designed double-blind placebo-controlled randomized clinical trials and meta-analyses. In this article, the therapeutic efficacy of AIT for allergic respiratory diseases, such as allergic rhinitis and asthma, is reviewed. In addition, potential clinical and experimental predictors of the treatment response are reviewed for AITs requiring long-term treatment, and for some allergic rhinitis and asthma patients who show no response to AIT. (Korean J Med 2020;95:370-376)
