The genetic approach to asthma has revealed a few candidate genes. Among them, special attention is given to the association between chromosome 5q and various cytokines and also to chromosome 11q and the IgE receptor. A mutation in chromosome 5 enhances interleukin-4 activity, which increases IgE synthesis by plasma cells. Polymorphism in the beta chain of the high-affinity IgE receptor (FC epsilonRI-beta) is considered to play a key role in the pathogenesis of asthma. Increased IgE, caused by both mutations, is responsible for inflammatory allergic reactions. A possible link between genetics and asthma has been suggested, although some studies could not confirm an association. Further study of the candidate genes may allow at-risk individuals to be tested and new treatments to be developed.