OBJECTIVES: Patients with allergic asthma not well controlled on pharmacotherapy constitute a significant cost to society, whilst having reduced quality of life. Allergy immunotherapy tablets for sublingual administration (SLIT-tablets) have been developed as an effective, well tolerated and convenient treatment modality, suitable for home treatment. The purpose of this analysis was to investigate cost-effectiveness of the SQ® HDM SLIT-tablet in a population with allergic asthma that is not well controlled, despite use of pharmacotherapy. METHODS: A multicentre, double-blind, randomised, placebo-controlled clinical trial with the SQ® HDM SLIT-tablet (ClinicalTrials.gov: NCT01433523) has shown statistically significant improvements for all efficacy endpoints in allergic asthma, including improvement in health-related quality of life. A cost-utility analysis was performed using a decision tree structure and data taken from the SQ® HDM SLIT-tablet clinical trial, including SF-36 and health care utilisation data. Long-term efficacy data was limited, and therefore conservative assumptions were adopted, framed by expert advice. As basis for the analysis, German preference weights and costs were applied and a 9-year time horizon adopted. Uncertainty around efficacy assumptions was explored by sensitivity analyses. RESULTS: The SQ® HDM SLIT-tablet was cost-effective compared with pharmacotherapy, in the treatment of allergic asthma (ICER<15,000 €/QALY). During sensitivity analysis, model results were sensitive to changes in input parameters, particularly in relation to long-term effectiveness. This indicates the importance of establishing long-term outcomes following treatment with the SQ® HDM SLIT-tablet. CONCLUSIONS: In the base case analysis, SQ® HDM SLIT-tablet proved to be cost-effective in the treatment of allergic asthma, compared to placebo. Conservative efficacy assumptions were adopted for the analysis, and therefore, the true benefits of the treatment may be underestimated.