Despite tremendous interest, the differences between the pathways leading to the dual response and those leading to the isolated early response are not completely understood. Understanding these differences is important for evaluating allergic diseases such as asthma and allergic rhinitis. In contrast to the more transient isolated early response, development of the late response is associated with the hallmark inflammatory features of chronic allergic disease. The combined cohorts represent a unique resource for the study of a fundamental physiologic response in allergy, and will provide genetic insight into new pathways for pharmacologic targeting in the treatment of chronic asthma and allergic rhinitis.