Back waist skin blackening common causes have waist pigmentation, if the waist has eczema or allergic dermatitis, local itching symptoms with hand scratching led to local pigmentation. It is recommended that local use of mometasone furoate ointment for local application, back waist fungal infection can also lead to waist skin blackening, and accompanied by peeling, itching, blisters and other symptoms, it is recommended that local use of terbinafine cream, ketoconazole nitrate cream for local application, in the hot summer if the back waist by serious ultraviolet radiation, resulting in local skin sunburn, easy to appear back waist skin blackening. When the kidneys have lesions will also appear back waist skin darkening, can be accompanied by varying degrees of pain, need to promptly go to the hospital for related checks, appear waist skin darkening if accompanied by obvious flaking, itching and other symptoms, need to promptly go to the hospital’s dermatology department.