The increasing development of new health care technologies, along with the ageing of the population and the increasing patients' expectations, cause a significant raise in medical costs, inducing in policy makers the need for well-funded information to support their decisions. The development of Health Technology Assessment (HTA), which is the systematic evaluation of properties, effects or other impacts of health technology and can be considered as a bridge between the world of research and the world of policy-making, reflects this high level of demand. HTA requires a multidisciplinary approach, that covers many different disciplines, in order to assess various aspects of health technologies, as technical properties, safety, efficacy/effectiveness, economic aspects, social, legal, ethical and political impacts. Allergic diseases show a worldwide increasing prevalence and consequent increasing costs, which result very high in recent evaluations. Specific immunotherapy is the only treatment able to alter, differently from drugs, the natural course of allergic diseases, exerting a long-lasting therapeutic effect, that persists also after stopping the therapy. This has a potential great impact in the cost of disease, which only recently was considered in properly designed studies. These issues claim for a larger use of HTA, which may provide a more comprehensive approach to the evaluation of the impact of immunotherapy on allergic patients.