The WHO (World Health Organisation) now classifies allergic diseases as the fourth most important disease in the world and estimates that these diseases represent "a major public health problem in terms of quality of life, days of work or of school missed, drug-related costs, or even mortality."

Over the last few decades, allergic respiratory diseases have become considerably widespread in the population, to the extent that they have reached record levels in western countries, where it is estimated that about one in four people have clinical symptoms of allergy. About 90 million Europeans and 65 million Americans are affected by allergic respiratory diseases. [1]

[1] Masoli et al. Allergy 2004; 59(5): 469-78; Aas et al. 1997 European Allergy White Paper: Allergic Diseases as a Public Health Problem, Leynaert JACI 2000,