BackgroundAllergic rhinitis (AR) is a chronic inflammatory disease of the upper airway, which progresses into allergic asthma (AA) in up to 45% of children. This analysis aimed to investigate clinical and economic benefits of sublingual allergen immunotherapy (SLIT tablets) initiated early in childhood for the treatment of AR by quantifying the long‐term reduction in new cases of AA.MethodsA Markov model was developed to estimate the long‐term effects of SLIT tablets on the risk of developing asthma. Key parameters were primarily based on data from the GRAZAX® Asthma Prevention trial and included the age‐ and treatment‐dependent risk of developing AA as well as annual probabilities of progression/remission in AR severity. Healthcare costs were estimated using data from the REACT study.ResultsIn a modelled cohort of children with moderate‐to‐severe seasonal AR initiated on SLIT tablets at ages 7 and 12, 24% and 29%, respectively, develop AA during a 20‐year period. In comparison, when initiated at age 5, 19% develop AA. Additionally, initiation of SLIT tablets at age 5 is associated with a total healthcare cost of EUR 20,429 per patient, whereas initiation at ages 7 and 12 is associated with, respectively, EUR 21,050 and EUR 22,379 per patient 20 years after AR diagnosis.ConclusionInitiation of SLIT tablets in early childhood is associated with a clinically meaningful and permanent reduction in new cases of AA and lower healthcare costs among children with AR. This finding supports the clinical relevance of initiating SLIT tablets early for children with AR to obtain long‐term clinical benefits.