Sublingual Immunotherapy for Allergic Rhinitis and Conjunctivitis

Giovanni Passalacqua; Valentina Garelli; Francesca Sclifò; Giorgio Walter Canonica


Immunotherapy. 2013;5(3):257-264. 

In This Article

Effects on the Natural History of Respiratory Allergy

SIT is recommended as part of the treatment for allergic rhinitis as an adjunct to the pharmacological treatment plan, in order to reduce symptoms and the need for rescue medications. This is named the 'immediate' or 'early' effect. Nonetheless, it is well known that rhinitis represents an independent risk factor for the subsequent development of asthma and none of the available drugs are capable of modifying this progression. On the other hand, SIT acts as a biological response modifier and induces profound changes in the immune response to allergens, meaning that it can affect the natural history of allergy in the long term.[54] This 'preventive' effect was firstly demonstrated with SCIT. In a randomized open controlled study, SCIT was able to significantly reduce the risk of developing asthma after 3 years of follow-up in allergic children with rhinitis only and this effect was maintained 7 years following discontinuation.[55] These results were subsequently replicated with SLIT. An open randomized controlled study involved 113 children suffering from seasonal rhinitis due to grass pollen, who were randomly allocated to medications plus SLIT or medications only.[56] After 3 years, 8/45 SLIT subjects and 18/44 controls developed asthma, with a relative risk of 3.8 for untreated patients. Another open prospective controlled study involved 216 children suffering from rhinitis with/without intermittent asthma.[57] They were randomly allocated 2:1 to drugs plus SLIT or drugs only, and followed for 3 years to detect the presence of persistent asthma. The prevalence of persistent asthma after 3 years was 1.5% in the SLIT group and 30% in the control group. The preventive and history-modifying effect of SCIT and SLIT are attractive and of potential clinical relevance, although the trials available so far are small, lack a placebo arm and are not double-blind. Thus, more robust data are required to draw a firm conclusion on this point.

Another important aspect concerning the effects on the natural history of respiratory allergy (not shared by standard pharmacological treatments) is the long-lasting effect after discontinuation. This effect has been seen in several SLIT studies in adults and children.[40,41,58–60] According to the literature, the beneficial effects are maintained for 2–6 years after discontinuation of SLIT, with an open study lasting 15 years. Nonetheless, a formal demonstration of this long-lasting effect would require prolonged double-blind controlled studies, which are not feasible from a practical viewpoint.