Sublingual immunotherapy: from safety to mechanism of action.

Allergen specific immunotherapy is an important option for the treatment of respiratory allergy and its clinical efficacy has been clearly demonstrated by several studies. However, the injective route of administration and the possibility of severe side effects has limited its use in children and led to the introduction of new forms of administration. Sublingual immunotherapy (SLIT) has proven to be an effective and safe treatment for respiratory allergy. However, its mechanism of action is still debated. Pharmacokinetic studies showed that, differently from nasal mucosa, allergen extracts administered by SLIT are not immediately adsorbed but are long retained before being drained to local lymph nodes. This difference may be responsible of the absence of severe side effects and instead of short-lasting local symptoms. Studies by biopsies of the oral mucosa should greatly help in defining the presence and the role of cells involved in the mechanisms of oral tolerance.