The current burden of allergic diseases, estimated by both direct and indirect costs, is very relevant. In fact the cost estimation for rhinitis amount globally to 4-10 billion dollars/year in the U.S. and to an average annual cost of 1089 euros per child/adolescent and 1543 euros per adult in Europe. The estimated annual costs in Northern America for asthma amounted to 14 billion dollars. Consequently, preventive strategies aimed at reducing the clinical severity of allergy are potentially able to reduce its costs. Among them, specific immunotherapy (SIT) joins to the preventive capacity the carryover effect once treatment is discontinued. A number of studies, mainly conducted in the US and Germany demonstrated a favourable cost-benefit balance. In the nineties, most surveys on patients with allergic rhinitis and asthma reported significant reductions of the direct and indirect costs in subjects treated with SIT compared to those treated with symptomatic drugs. This is fully confirmed in recent studies conducted in European countries: in Denmark the direct cost per patient/year of the standard care was more than halved following SIT; in Italy a study on Parietaria allergic patients demonstrated a significant difference in favor of SIT plus drug treatment for three years versus drug treatment alone, with a cost reduction starting from the 2nd year and increasing to 48% at the 3rd year, with a highly statistical significance which was maintained up to the 6th year, i.e. 3 years after stopping immunotherapy, corresponding to a net saving for each patient at the final evaluation of 623 euros per year; in France a cost/efficacy analysis comparing SIT and current symptomatic treatment in adults and children with dust mite and pollen allergy showed remarkable savings with SIT for both allergies in adults and children.