Erythema nodosum is an inflammatory disease that occurs in the subcutaneous fat, and the main symptoms include typical symptoms of the skin, systemic symptoms, and it is recommended that the relevant people seek timely medical treatment. 1. Typical symptoms. It is characterized by the appearance of red or purplish-red nodules in batches, accompanied by pain, the number of which varies from several to dozens and is mostly distributed symmetrically, and it mainly occurs on the extensor surfaces of calves, and can be seen on the thighs, forearms, face, neck and trunk, etc. In the early stage, the nodules are smooth and smooth. At the beginning, the nodules are smooth and slightly higher than the skin surface; after a few days, the nodules flatten out and leave a greenish-purple plaque; about 3-6 weeks later, they can subside on their own and leave no traces. 2. Systemic symptoms. Fever, fatigue, joint and muscle pain, etc. may appear before the appearance of the rash. It is recommended to consult a doctor to identify the cause of the disease and carry out targeted treatment.