Specific immunotherapy is the only treatment targeting the causes, and not only the symptoms, of allergic diseases. Sublingual immunotherapy (SLIT) was introduced and developed to solve the problem of the adverse reactions, uncommon but possibly severe and rarely fatal, to the traditional subcutaneous immunotherapy (SCIT). The evidence of SLIT efficacy concerns rhinitis and asthma caused by sensitization to pollens and to house dust mites, but there are increasing data suggesting that SLIT could be applied in forms of allergy hardly feasible for SCIT because of its poor safety (this is true for food allergy and latex allergy) or could be considered for new applications, such as atopic dermatitis or baker's asthma. In particular, there are placebo-controlled trials indicating good efficacy and safety of SLIT in patients allergic to latex and to foods and in children with atopic dermatitis, that indicate SLIT as a real treatment option in such clinical entities. This article also discusses some patent related to the field.