Abstract: Allergic asthma represents one of the most prevalent chronic inflammatory airway disorders in the pediatric population, with a persistently rising prevalence among Chinese children aged 0–14 years. House dust mites constitute the predominant inhalant allergens, yet symptom control through environmental avoidance measures alone remains largely insufficient. Although conventional maintenance therapies can ameliorate clinical manifestations, they do not fundamentally modify the underlying immunological derangements. Subcutaneous immunotherapy (SCIT) currently stands as the only disease-modifying intervention capable of altering the natural history of allergic diseases, and its application in pediatric allergic asthma has a well-established clinical track record. Nevertheless, considerable uncertainty persists in routine practice regarding optimal candidate selection, treatment duration, and long-term efficacy prediction. This review synthesizes current advances in the immunomodulatory mechanisms underpinning SCIT and summarizes available evidence on clinical effectiveness, safety profiles, and combination therapeutic strategies in children with allergic asthma. We further focus on how distinct sensitization phenotypes influence treatment responses, comparing differential outcomes—including symptom alleviation, pulmonary function improvement, and sustained disease control—between mono-sensitized and polysensitized patients, while exploring potential contributors to observed variability. In parallel, we highlight the emerging role of component-resolved diagnostics in refining patient stratification and enabling individualized regimen design, and critically assess whether this technology can improve therapeutic decision-making in polysensitized children. Through this analysis, we identify key methodological shortcomings in the existing literature: the predominance of single-center studies with limited sample sizes, the absence of uniformly applied definitions for polysensitization across trials, and the lack of standardized assessment frameworks tailored to specific sensitization patterns. By integrating current evidence with a critical appraisal of persisting challenges, this review aims to provide a practical reference for optimizing SCIT implementation and advancing personalized management strategies in pediatric allergic asthma.