Efficacy of sublingual immunotherapy in asthma and eczema

Sublingual immunotherapy (SLIT) is the local route of administration of allergen extracts investigated in several controlled clinical trials. In a number of countries, particularly Italy, France and Spain, this has become common in office practice. At variance with subcutaneous immunotherapy, the knowledge of mechanisms of action of SLIT is still at the beginning: some studies, in animal models, provided interesting information: the dendritic cells of oral mucosa act as efficient antigen-presenting cells and produce IL-12, which directs the immune response towards a Th1 profile away from IgE-Th2 profile. Its clinical efficacy (improvement of symptoms and reduction of drug intake) for both asthma and rhinitis has been assessed in detail for the most common allergens: house dust mites, grass pollen, Parietaria, birch pollen and olive tree. SLIT requires further evaluation concerning the treatment of the extrinsic form of atopic dermatitis. The induction of immunologic tolerance rather than immunoreactivity should be worth pursuing due to the immunologic pathway involved in the pathophysiology of atopic dermatitis. The safety profile of SLIT, derived from the clinical trials and postmarketing surveillance studies, turned out to be satisfactory in adults and children. SLIT represents an important step towards an efficacious and safe treatment of patients with allergic respiratory diseases; nevertheless, further studies are necessary to establish it as a viable alternative to subcutaneous immunotherapy.