It is a red lump on the root of the thigh and is considered to have the following two diseases: 1. Tinea corporis is mainly caused by fungal infection and can form a ring of erythema with raised edges and a fading center, accompanied by itching, and is mainly caused by fungal infection. 2. Acute febrile neutrophilic dermatosis may appear as painful red nodules or plaques, accompanied by fever as a feature, histopathological examination can help clarify the diagnosis, in clinical treatment preferred glucocorticoids, should be carried out under the guidance of a doctor.