There are many diseases with black spots growing on the back area, you need to carefully observe the skin appearance, if the black spots are distributed in patches, not painful or itchy, there is no obvious bump when touched by hand, you can see fine flakes on the surface, consider it to be tinea pedis formed after fungal infection, also called sweat spot, you can do fungal test to clarify the diagnosis. If the black spots are dotted, it is considered to be pigmentation spots secondary to folliculitis in the back area. Local application of clear hydroquinone cream for treatment has a very good improvement effect, or you can choose to use Q1064 laser, which can accelerate the pigmentation like fading. If the pigmented spots have raised and keratosis-like tissue can be felt on the surface, it is considered seborrheic keratosis, which can be removed by freezing or laser.