The allergen specific immunotherapy is the administration, in IgE-mediated allergic patients, of a specific allergen in a gradually increased number to provide protection against allergic symptoms and inflammatory reaction. The current immunotherapeutic approaches occur by modulating the release of inflammatory mediators involved in allergic reaction and consequently the inhibition of allergic inflammatory process. Since 1997 several World Associations of Allergy, Asthma and Immunology, have reviewed this issue, seeking to establish standards for its use. Also many publications about the immunotherapy’s efficacy, as well as, several guidelines on the use of immunotherapy in the treatment of allergic are available. This article will focus on the most current evidence about the immunotherapy in allergies regarding its mechanism of action, effectiveness and practical considerations.