Purpose of the Review: To analyse the evidence regarding the optimal duration of subcutaneous and sublingual immunotherapies to induce long-lasting benefits after treatment cessation for allergic rhinitis and asthma and to identify unmet needs.

Recent findings: Subcutaneous and sublingual immunotherapies are highly effective in desensitising selected subjects with allergic rhinitis and allergic asthma. Double-blind, placebo-controlled, randomised clinical trials of both routes of immunotherapy support international guidelines that recommend their use for at least three years to achieve disease modification and continued clinical and immunological tolerance for allergic rhinitis. Evidence of the long-term effects of allergen immunotherapy in the context of randomised controlled trials for allergic asthma as opposed to rhinitis is limited. Nonetheless, real-world studies suggest the long-lasting benefits of allergen immunotherapy for allergic asthma, as this reduces prescriptions for pharmacotherapy and decreases the risk of asthma exacerbations and hospitalisations. The GINA guideline 2023 recommends the use of house dust mite sublingual immunotherapy as an add-on therapy in subjects with suboptimally controlled asthma, despite the use of low to high doses of inhaled corticosteroids, provided that the FEV1 is >70% predicted.

Summary: Robust clinical trials of subcutaneous and sublingual immunotherapies have shown that 3 years of continuous treatment modifies the underlying course of allergic rhinitis with long-lasting clinical effects years after withdrawal. Further evaluations of the long-lasting effects of novel routes of allergen immunotherapy for allergic rhinitis and long-term studies for allergic asthma are needed in the context of randomised clinical trials.