Sublingual immunotherapy (SLIT) currently represents, as indicated by meta-analysis of its efficacy and safety, a valid option to the generally used traditional subcutaneous immunotherapy (SCIT) for treating respiratory allergy. Regarding efficacy, recent studies demonstrated that, similar to what has already been observed in SCIT as well as in experimental and clinical studies about the magnitudo of allergen exposure, the effectiveness on both clinical symptoms and immunologic changes depends on the amount of allergen administered during treatment. In addition, in vitro studies addressed with the role of dendritic cells, currently considered to be of pivotal importance in orienting toward tolerance the immune response to allergens, showed that the internalisation of allergen molecules, which is followed by tolerogenic presentation to T cells, depends on the amount of allergen. However, such dose dependence is not apparent concerning the safety. In fact, the comparison of studies respectively conducted with high and low allergen doses did not show differences in the rate of systemic reactions, which in any case never had the presentation of anaphylaxis, and instead a significant difference in the rate of local reactions, following the oral and gastrointestinal contact with the allergen extract, in favour of high dose studies.