Allergic Diseases in the Elderly.

Recent increases in allergic diseases are thought to be caused by better hygiene, Westernized diets, air pollution, climate change, and other factors that influence host microbiota, a key player in the induction and maintenance of immunoregulatory circuits and tolerance. The increase of allergic diseases in the elderly is also related to additional factors, such as various comorbidities that may interfere with the development and the type of allergic reactions. Immunosenescence plays a central role in these reactions, altering microbiota responses and triggering inflammageing. In addition, in the elderly, there is a shift from Th1 to Th2 immunity, thus favoring allergic responses. A better understanding of the mechanisms responsible for immunosenescence and its effects on allergic inflammation will most certainly lead to improved therapies.