A large dark circle of skin on the waist may be caused by herpes zoster, previous inflammation, skin friction and other conditions. 1. Herpes zoster: may be due to infection with varicella zoster virus caused by herpes zoster, the acute stage is usually manifested as a band of erythematous blisters, may be left after the subsidence of brown pigmentation. 2. Previous inflammation: If the waist has chronic inflammatory stimuli, such as fungal infections or eczema, etc., due to repeated scratching and the use of drugs, will lead to skin pigmentation in the area. 3. Skin friction: If the patient wears underwear that is too tight, it may lead to repeated friction between the underwear and the skin of the waist, which will easily lead to the phenomenon of darkening of the skin of the waist. It is recommended that the patient should consult the doctor in time to get a clear diagnosis and strictly follow the doctor’s instructions for treatment.