Allergy is on the increase worldwide. Today people are becoming more and more aware about the allergens and the Sublingual Immunotherapy (SLIT). Allergens are molecules with capacity to elicit IgE responses in human (reactive antibodies induce allergy symptoms). Identifying causative allergens and feeding allergy subjects in small quantities through Sublingual route (SLIT) on daily basis over a period of time induce tolerance in the body by producing blocking antibodies (IgG), which reduces
the allergy symptoms. Sublingual immunotherapy emerged in the year 1980 in the midst of safety issues of traditional century old subcutaneous immunotherapy (SCIT). Study by Scadding and Brostoff introducing Sublingual immunotherapy (SLIT) with very low doses and followed by another controlled trial after a gap of four years. A major turn on first metaanalysis evaluating the data from the first 22 controlled studies, demonstrated the efficacy and safety of SLIT in seasonal allergic rhinitis. Now, the studies of dose-response clearly demonstrate that the clinical efficacy of SLIT depends upon the administrated dosage, as already proved since long time for SCIT. Systematic revision of the literature showed that SLIT has no dose dependence of safety, which allowed the development of new formulations of SLIT without up dosing phase. SLIT is considered a suitable alternative to injections.