Symptom and medication use are the key outcomes for assessing the efficacy of subcutaneous (SCIT) and sublingual allergen immunotherapy (SLIT). Our objective was to explore the similarities and differences between existing scoring mechanisms used in clinical trials of SLIT for seasonal allergens and characterize the impact that such differences may have on efficacy reporting. Randomized, double-blind, placebo-controlled clinical trials investigating the efficacy of SLIT for seasonal allergic rhinitis (2009-2013) were selected for review. Simulated and published data were used to demonstrate differences in scoring methods. Symptom and medication scoring methods across trials, although all designed to achieve the same objective, included important differences. The maximum daily symptom score (DSS) can vary widely depending on the number of symptoms assessed, and terminology of symptoms is not consistent. Similarly, daily medication scoring (DMS) methods differ greatly among studies and are dependent on medications allowed and weighting of scores assigned to each medication. When published DSS and DMS scores were used to calculate simulated daily combined scores (DCSs) based on various published methods, changes from placebo ranged from 19% to 29% when assuming all variables other than the DSS and DMS methods were equal. Variations in trial design, analysis, and seasonal characteristics also have effects on symptom and medication scoring outcomes. We identified multiple differences in trial scoring methods and design that make comparison among trials difficult. Symptom, medication, or combined scores cannot be indirectly compared among trials without taking the methods of scoring and other trial differences into account.