Sublingual immunotherapy: the optimism and the issues.

The acceptability of sublingual immunotherapy (SLIT) in guidelines or statements has recently increased. SLIT is currently used in Europe, Asia, and Australia for the treatment of allergic respiratory diseases. Four meta-analyses have shown that SLIT is an effective tool for the treatment of patients with asthma and/or rhinitis, and only conflicting results were reported for children with allergic rhinitis. Moreover, it offers logistic advantages and is safe. However, some unmet needs are to be faced, such as the difficulty of manufacturers to achieve the homogeneity of standardized vaccines, the magnitude of their clinical efficacy, and the pivotal question of an early intervention with SLIT in young children with IgE-mediated disorders. Altogether, SLIT has already given convincing results in respiratory diseases both in adults and children. In the future, this route of administration of allergic vaccines may improve even the treatment of patients with IgE-mediated food allergy. These patients indeed deserve better than allergen avoidance. The immunomodulatory treatment of allergic diseases probably has found a new tool; however, a more balanced understanding of this form of allergen immunotherapy is needed. This aim could be achieved through: (1) the improvement of products standardization quality; (2) an attempt to modify in children the natural course of allergic diseases; and (3) new research on mechanisms of action.