The IL-9 gene maps to the long arm of chromosome 5 (5q31–35), which also contains genes encoding IL-4, IL-5, and IL-13.21 In allergic asthma, polymorphisms in this region are significantly associated with the development of atopy, bronchial hyperresponsiveness, and elevated total IgE levels.22–24. Here, IL13 is linked to allergic asthma.