Asthma is a chronic inflammatory disease of the lung. It occurs as a result of inappropriate type 2 – dominated immune response to environmental allergens. Cytokines (IL4, IL5 and IL13) have been shown to regulate the pathological features of the disease, including airway hyper-responsiveness (AHR), eosinophilic pulmonary inflammation, airway remodeling and IgE synthesis. Regulatory T-cells are thymus derived population of CD4+ T-cells. An understanding of its mechanism in allergic disease may lead to development of effective therapeutic strategies for treatment of disease.