Is sublingual immunotherapy clinically effective?

Sublingual immunotherapy has become increasingly popular and in some countries more allergic patients are treated by the sublingual route than the subcutaneous route. Evaluation of the scientific documentation for clinical efficacy is important before a treatment is used without restriction. This review critically analyses every placebo-controlled, double-blind study providing symptom/medication scores for the primary outcome; that is, a significant and clinically relevant reduction in disease severity of actively treated patients.

In total 23 papers fulfill the evaluation criteria; 26% are categorized as unequivocally effective, 35% are possibly effective (significant improvement in either symptom or medication scores), and 39% have no statistically documented efficacy.

The majority of papers have used an inadequate study design that may be responsible for the large number of inconclusive and negative studies. Before sublingual immunotherapy can be recommended as a routine treatment, more documentation for beneficial efficacy is needed.