It is believed in TCM that the lung and the large intestine collaborate physiologically with each influence each other pathologically, and both are correlated to the skin and hair directly or indirectly. Urticaria is a common seen allergic dermatitis, and its treatment is closely relevant to the theory of “exterior-interior relations of lung and large intestine”. The link is not only can be seen in the pathogenesis but also can be seen in the clinical treatment. The theory is widely used in the prevention and treatment of dermopathic disease, and more over, it can be instructive to the therapy of exogenous disease and internal miscellaneous disease.