The use of allergen Specific Immunotherapy (SIT) to treat allergic asthma is still a matter of scientific debate. Currently, there are few studies specifically designed to evaluate asthma, and few studies had a formal sample size calculation, or objective parameters of pulmonary function assessed. On the other hand, there are good quality trials with both Subcutaneous Immuno-therapy (SCIT) and Sublingual Immunotherapy (SLIT) in allergic rhinitis, where asthma symptoms were also evaluated, if present. These studies consistently reported positive results. Moreover, several favourable meta-analyses are available, although their validity is limited by the great heterogeneity of the trials included. The disease modifying effect of SIT that is the capacity of preventing asthma onset should be also taken into account.
Concerning the safety, fatalities seem to be an exceptional event, and in Europe no fatality has been reported over the last two decades. Uncontrolled asthma is universally recognized as the most important risk factor for severe adverse events.
In conclusion, both SLIT and SCIT can be used in asthma associated with rhinitis (which is the most common condition), provided that asthma is adequately controlled by pharmacotherapy. In such case, a measurable clinical benefit on asthma symptoms can be expected. Nonetheless, SIT cannot be presently recommended as single therapy when asthma is the unique manifestation of respiratory allergy.