With the approval of sublingual allergen-specific immunotherapy (SL-AIT) tablets for grass and ragweed pollen by the Food and Drug Administration, SL-AIT is gaining traction in Europe, the United States, and other places. Based on what has been published since January 2014 on subcutaneous-versus-SL-AIT effectiveness, safety, and other concerns, researchers evaluated issues linked to the selection of patients for the sublingual or subcutaneous route for allergic individuals. As patient adherence appears to be one of the primary issues in real-life AIT, researchers have tried to improve AIT simplicity by shifting to home-administered SL-AIT and shortening the subcutaneous-allergen-specific immunotherapy (SC-AIT) build-up or maintenance phase. The latter was safe due to the presence of various hypoallergenic extracts. In terms of SL-AIT, double-blind placebo-controlled major studies in patients with allergic rhinitis and asthma, particularly in adults, have demonstrated the effectiveness and safety of ragweed pollen and house dust mite SLIT tablets and highly concentrated liquid formulations. A major trial of SLIT in 3-year-old children proved successful.

With the advancement of SL-AIT efficacy, the choice of SC-versus-SL-AIT will most likely be based on practical considerations rather than efficacy, while keeping in mind which SL-AIT products have demonstrated efficacy.