Asthma is an inflammatory condition of the bronchial airways. This inflammation causes the normal function of the airways to become excessive and overreactive, thus producing increased mucus, mucosal swelling and muscle contraction. (American Lung Association, 2008). In 2000, Yssel and Groux defined asthma as a complex and heterogeneous disease that is characterized by intermittent reversible obstruction and chronic inflammation of airways, bronchial hyper reactivity and an infiltration of lymphocytes and eosinophils to the airway submucosa. IL-18, formerly called interferon (INF-gamma) inducing factor, is a novel proinflammatory cytokine related to the IL-1 family (Wong, et al, 2001). IL-18 is known to be a potent inducer of Th1 cell-mediated responses, although it can also induce Th2 cytokines and IgE production, and cross regulates Th1and Th2 responses (Ando & Shima, 2007). From these result, it was deduced that Il-18 may act as a coinducer of Th1 and Th2 cytokines (Tanaka, et al, 2000). IL-18 may be an important cytokine for initiating and perpetuating the catabolic and inflammatory response in allergic asthma .It also act as a coinducer of the Th2 cytokine IL-4, IL-10, IL-13 and histamine from T Cells and basophils, respectively, and contribute to CD4+ t cell-independent and IL-4 independent IgE production (Wong, et al, 2001).