Sublingual immunotherapy: what lessons can we draw from recent studies?

Abstract

Allergen-specific immunotherapy, together with drugs and allergen avoidance, is a cornerstone in the management of respiratory allergy. The traditional subcutaneous route is burdened by the risk of severe adverse events; therefore, safer routes of administration (e.g. local routes) have been developed and are being investigated. Controlled clinical trials have failed to demonstrate the clinical efficacy and the safety of oral or bronchial administration, and these routes have been abandoned. Local nasal immunotherapy proved effective and safe in 17 of 18 controlled trials; thus it could be considered to be a viable route of immunotherapy. Nevertheless, nasal immunotherapy is effective in rhinitis only and requires a particular administration technique; therefore, its use is slowly declining. In contrast, the efficacy of sublingual administration in the treatment of asthma and rhinitis in adults and children is supported by numerous controlled trials. The safety profile, assessed in clinical trials and post-marketing surveillance studies, is satisfactory; the most frequent side effects are gastrointestinal complaints, which can be easily managed by proper adjustment of the dose. The World Health Organization now considers sublingual immunotherapy as a valid alternative to the subcutaneous route, including its use in children. The long-lasting efficacy of treatment via the sublingual route has been documented recently but a number of points still need to be investigated, including mechanisms of action, optimal dosage, cost-effectiveness and patient's adherence.