Sublingual immunotherapy in allergic rhinitis and asthma: A review of recent clinical evidence

A growing body of evidence is accumulating in support of sublingual immunotherapy (SLIT) for the treatment of allergic rhinitis and asthma. Several European countries use SLIT in preference to the more established subcutaneous immunotherapy (SCIT) because of improved safety and ease of administration, particularly among children and those with asthma. However uncertainty persists, particularly in the United States where SCIT is widely accepted and utilized, and SLIT is still subject to review. Contributing to this uncertainty is the apparent between-trial heterogeneity regarding efficacy; a lack of understanding regarding the mechanism of action; failure to define optimal allergen doses; and, until recently, the lack of evidence demonstrating satisfactory patient compliance with this home-based treatment. In the following review we look at conclusions drawn from trials conducted before 2003 and examine newer evidence obtained from recent trials recruiting larger cohorts. Our aim was to summarize the evidence presented in the medical literature, to address questions arising from these studies, and to determine whether the most recent evidence supports the contention that SLIT can be considered as a valid alternative to SCIT in allergic rhinitis and allergic asthma. In response to suggestions that between-trial heterogeneity might stem from differences between allergens prepared by different companies or arise as a consequence of limited cohort size, we present the evidence with clear distinction between trials according to source of allergen preparation and where possible examine studies based upon relatively large cohorts.