Allergic asthma affects over 100 million people worldwide and more than 20 percent of Canadians. Furthermore, it is increasingly prevalent among people living in industrialized countries. While the underlying cause(s) of asthma remain unknown, there is increasing evidence to suggest that the intestinal microbiota (normal flora) plays an important role in the development of atopic diseases. Data from several large birth cohort studies have indicated that there may be a strong association between alterations in the intestinal microbiota as a result of antibiotic use and increases in the incidence of allergy and asthma in young children. However, the role of the intestinal microbiota in asthma has not yet been explored experimentally, and no attempts have been made to identify microbial species that may be associated with or hinder the development of asthma. Consequently, Shannon Russell is researching how changes in the composition of the intestinal microbiota may induce changes in asthma susceptibility. She is doing a series of experiments designed to determine whether antibiotic treatment during the early stages of life may alter or delay normal immune development and predispose a person to allergic-type diseases like asthma. This research could establish entirely new roles for the intestinal microbiota and may ultimately aid in the development of novel therapies (e.g. probiotics, prebiotics, narrow spectrum antibiotics), to treat or prevent allergic diseases including asthma.