Case Lv, female, 53 years old, was first diagnosed on April 17, 2003. Complaint: fever with redness, swelling and heat pain in the left lower limb for 3 days. History: The patient developed a high fever (T 39.2℃) 3 days ago without any obvious cause, and later developed redness and burning pain in the left lower extremity. The patient had a history of tinea pedis. The patient had a history of athlete’s foot. Physical examination: swelling from the dorsum of the left foot to the upper middle third of the calf, red and red skin with clear borders, subcutaneous purpura seen in front of the shin, burning on the palpation and obvious tenderness. The tongue is red, the coating is yellow and greasy, and the pulse is stringent. Physical and chemical examination: WBC 12*10?9/L, N 79.6%, L 17.4%. Diagnosis: flowing fire, evidence of damp-heat and toxic deposits. Treatment: Cool the blood to clear heat, detoxify and resolve blood stasis, and adjuvantly promote dampness to eliminate swelling. Formula: “Rhizoma Rhizoma Dihuang Tang” combined with “Si Miao San” plus and minus. On April 24, the fever had subsided, the redness and burning of the skin of the left lower extremity had subsided, there was pigmentation in front of the shin, the swelling was still mild, the tenderness was not obvious, and the stool was clear. Blood WBC 6.1*10?9/L, N 57%, L 17.4%. Considering that the heat toxin has basically gone, the treatment is intended to activate the blood and clear the ligament, and add strengthening of the spleen and dampness to reduce swelling. Dangxian is an acute reticulolymphatic inflammation caused by group A beta streptococcus. Clinically, it is characterized by sudden onset of the disease, malignant chill and fever, sudden localized redness of the skin, coloring like dan-painted fat, {heat swelling, rapid expansion, and indefinite occurrence. The disease can be clinically divided into erythematous dermatitis, purpuric dermatitis, herpetic dermatitis and necrotizing dermatitis. The “Sheng Ji General Record” cloud “heat poison gas, burst in the skin, can not be drained, the heat is stored for Dan Poison.” The etiology of dermatophagoides is always caused by heat in the blood, external wind, dampness and heat, or skin and mucous membrane injury, and the invasion of evil, dampness and heat, and fire, which is not allowed to drain inside, and depressed in the skin, and the disease occurs outside. The lower extremity of Dan Poison, also known as flowing fire, more and more damp-heat, dampness is swollen, heat is red, fire poisoning, fire breaks blood delusion, blood overflow outside the veins, then see the purpura under the skin, damp-heat contains blocked meridians, not pass is pain, so the internal treatment of flowing fire is appropriate to cool the blood and clear heat, detoxification and remove blood stasis, accompanied by dampness to reduce swelling.