When black patches appear on the skin, you need to carefully observe the appearance of the black patches. If the black patches are flat against the skin and there are mild flakes on the surface with white patches, consider it to be lichen planus resulting from fungal infection, which is not painful or itchy, and can be treated with oral terbinafine tablets and topical sertaconazole nitrate cream. If the black patches are purely secondary to eczema and dermatitis, it is considered to be pigmentation, which is caused by the local proliferation of skin pigment cells, and it is not necessary to pay attention to it, and it will gradually fade away with time. If the black patches have roughness on the surface with itching, it is considered as skin amyloidosis, and it is recommended to choose compound lactic acid cream with fluticasone propionate cream for treatment.