Risk factors for asthma in adolescents in a large urban region of Brazil.

Background: Identify risk factors for asthma in adolescents from São Paulo, Brazil.

Methods: total of 528 adolescents (141 asthmatics, 387 control subjects) from the ISAAC study (phase III) were submitted to a complementary questionnaire to evaluate risk factors, through response to questions regarding personal history, environment, and diet and an agreement to undergo the skin prick test (SPT) for aeroallergens.

Results: Positive SPT to at least one allergen occurred in 49.