Objectives -- General approach and layout of the book -- Exacerbation of asthma, experimental evidence -- Exacerbation of asthma, epidemiological evidence in adults -- Exacerbation of asthma, epidemiological evidence in children -- Exacerbation of asthma, overall assessment -- Induction of asthma, methods and general considerations -- Induction of asthma, evidence in non-smoking adults -- Induction of asthma, evidence in children -- Induction of asthma, overall assessment -- Final conclusions.