Erythema nodosum is a kind of lipomatous membrane inflammation characterized by delayed-type hypersensitivity reaction, which can be consulted in dermatology and rheumatology and immunology. 1. Erythema nodosum is a form of lipomatous membrane infection caused by dermal vasculitis and lipomatous membrane inflammation, with painful nodules on the lower extremities as the main clinical manifestation. Many factors can trigger the disease, such as infection, drug exposure, tuberculosis, inflammatory bowel disease, pregnancy and malignancy. There are also many cases where the cause of the disease is unknown. 2. Erythema nodosum is generally recommended for further evaluation and treatment in a dermatologist. However, for recurrent flare-ups and suspected underlying diseases, or when additional systemic investigations are needed for evaluation and intervention, referral to appropriate specialties such as rheumatology should be made for further evaluation. The causes of erythema nodosum are complex, and it is advisable to seek prompt medical attention for further investigations to determine the cause of the disease and to provide targeted management or treatment.