Tinea corporis is a contagious ringworm that occurs in the groin, upper inner thighs, and vulva. The causative agent of ringworm is a fungus, and the most common ones in China are Trichophyton rubrum, Trichophyton spp. and Trichophyton flocculentum. When the disease first appears, papules or small erythematous patches occur on the upper inner thigh, groin, or side of the vulva, which flake off and gradually expand and spread in all directions, forming a ring or semi-ring with clear borders, and papules, blisters, and flaking are evident at the borders, while the central part can heal on its own. In long-standing cases, skin hypertrophy and hyperpigmentation may occur, spreading to the opposite side, perineum, perianal area, buttocks, and even scrotum, penis, and mons pubis. The disease is often accompanied by significant itching, and scratching by the patient can lead to infection and secondary bacterial infection. If the above symptoms occur, you should go to the dermatology department in a timely manner. Generally, a fungal test is required to confirm the diagnosis of the disease, and then topical or oral antifungal medication is given according to the specific condition. I often see a lot of patients in the clinic when the above-mentioned symptoms, to buy their own pharmacy to “skin easy”, “dermatitis flat” and other hormonal drugs to apply, not only can not cure the disease, but the more you apply the more extended, resulting in aggravation of the disease, and even cause complications. Since fungi thrive in warm and humid environments, prevention of the disease requires the following: keep the body dry and clean, especially between the thighs, groin, vulva, anus, etc.; wear less thick and tight underwear and pantyhose; change and dry underwear and clothing frequently; bathe and dress promptly after sweating from exercise or rain to keep dry; and treat ringworm in other parts of the body promptly. If one of the spouses is infected, they should stop having sex temporarily until they are cured so as not to infect the other spouse; sitting toilets are one of the ways to spread ringworm, and special care should be taken when using sitting public toilets.