This disease refers to a vasculitis localized in the subcutaneous tissues and deep layer of the dermis and occurs mostly in young females in spring and autumn. The etiology of this disease is complicated and it is mainly caused by streptococcus infection in the upper respiratory tract and can also be caused by tuberculosis, virus, chlamydia and fungus. In addition, rheumatoid arthritis, intestinal diseases, tumors or medications can also be the causative factors of this disease. The pathogenesis is still unknown and may be a kind of delayed allergic reaction or disease of immune complex. This disease is similar to"Multiple Abscess of Damp Toxin" and "Gua Teng Chan (Erythema Nodosum)" in Chinese medicine, induced and repeatedly broken out by production of fire due to long accumulation of dampness, obstruction of the meridians and collaterals due to downward transmission of dampness and heat, or by blockage of the meridians and collaterals due to long-term sickness, leading to qi stagnation and blood stasis.