Allergic cutaneous nodular vasculitis is a type of skin disease that is based on the inflammation of small blood vessels in the subcutaneous tissue of the lower extremities and results in nodular lesions. Allergic cutaneous nodular vasculitis can be seen in a variety of diseases such as leukoaraiosis, rheumatic diseases, nodular lipofuscinosis, profound lupus erythematosus, erythema nodosum, nodular vasculitis, etc. Erythema nodosum is one of the most common allergic cutaneous nodular vasculitis, characterized clinically by painful nodules in the lower legs, caused by many different pathogenic factors (bacterial and viral or fungal infections, certain drugs, malignant tumors, abnormal body immunity, etc.). Some patients have symptoms such as cold, fever and arthralgia before the onset of the disease. Erythema nodosum can occur at any age, but it is more common in 20-40 years old, and the incidence of female patients is 3-6 times that of male patients. The disease can recur and affect the life of patients. The typical manifestation of erythema nodosum is hard, round, oval or curved nodules with obvious tenderness and unclear borders, usually occurring in the front of the lower leg, with asymmetry on both sides. Laboratory tests indicate accelerated blood sedimentation and elevated C-reactive protein, and some patients have elevated white blood cell count. Treatment: Non-steroidal anti-inflammatory drugs such as salicylates are often used clinically. Patients with clear causes of infection can use antibiotics appropriately, and oral potassium iodide is effective, but many hospitals do not have such drugs and are prone to relapse when they stop. Some doctors like to use glucocorticoids, which are fast-acting, but easy to relapse and more difficult to treat after stopping. In our treatment of most patients, we found that the combined use of blood-activating drugs such as compound Danshen tablets has obvious adjuvant effect and shortens the course of the disease.