Ringworm on the inner thighs of men is tinea cruris, which is mainly caused by fungal infection, and environmental factors also easily lead to the occurrence of tinea cruris. Fungus and the body of the skin contact, can adhere and penetrate the stratum corneum cells, at the same time will secrete inflammatory mediators, and the body of the fungus to provide a favorable growth environment, such as the skin barrier is damaged, the temperature and humidity, etc., and ultimately lead to the occurrence of tinea versicolor, the red trichophyton is the most common. Unhealthy living habits can easily lead to the appearance of ringworm, such as clothes are not breathable, wearing wet clothes for a long time, sweating more, sharing towels and other daily necessities with others, etc., and being in a hot and humid environment for a long time. It is recommended that patients seek timely medical treatment, confirm the cause of the disease under the guidance of the doctor, avoid it in time, and receive standardized treatment as soon as possible.