Asthma is a complex respiratory disorder of inflammatory origin, whose onset and progression are influenced by numerous elements, such as genetic, environmental and ethnic factors as well as socio-economic conditions. The characteristics of asthma vary from person to person; it is manifested by different responses to a variety of triggers and therapies. Recognizing the heterogeneity of asthma and its relative characterization aids in determining an appropriate and specific treatment therapy for each patient.
Different hypotheses have been put forth to explain the increasing diffusion of asthma and other allergic diseases in western countries since the 1970’s: some regard hygiene and intestinal microbiota, while others propose a connection between vitamin D status and the development of asthma, wheezing, allergic rhinitis, food allergies and atopic dermatitis. The International Study of Asthma and Allergies in Childhood (ISAAC) analyzed the connections between the role of westernization – a lifestyle in which we spend more time indoors with resulting vitamin D deficiency – and the increase of cases of asthma and allergies. The study found a very high incidence of asthma symptoms in countries such as the UK, Australia, New Zealand and Ireland. Some studies carried out in several Chinese cities with different socio economic profiles have shown a prevalence of asthma and allergic symptoms in Hong Kong, the most westernized city among those analyzed.