This meta-analysis compared treatment adherence (discontinuation rate) and safety (adverse events) between subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT) in patients with allergic rhinitis. It included randomized controlled trials selected from databases from inception to August 2025, with quality assessment according to the Cochrane RoB-2 tool and analyzes in RevMan 5.3 and STATA 18.0. There was no statistically significant difference in discontinuation rates between SCIT and SLIT (combined log OR = 0.30, 95% CI [−0.79, 1.39]). The incidence of adverse events was significantly higher with SCIT than with SLIT (pooled log OR = 0.60, 95% CI [0.05, 1.15], p = 0.03). Both methods showed comparable adherence, but SLIT had an advantage in safety. Clinical decisions should take into account patient preferences, comfort, and monitoring. Long-term studies with large samples are needed for confirmation.