Black patches on the back are typically identified as Mongolian spots. Depending upon your age, they could be permanent or not. Usually, Mongolian spots appear on the surface of the skin at birth and fade away by age five. These are black or deep brown, in some cases, even deep blue patches that appear on the back and buttocks of the child. They actually look like a very bad and deep bruise, but are not bruises. Mongolian spots are always harmless, and do not cause any harm, pain or problem to the child. If they do not fade away by the time a child is five, then they become permanent, and are passed off as birth marks in adulthood. You can decide if what you have on your back are Mongolian spots. If you do not know for certain, however, it is best to go for a medical examination to determine what exactly these spots are and whether they will be harmful or not.
For large part, there is no cure or remedy of any kind available to remove Mongolian spots. The only answer would possibly lie in skin surgery, since this colour, if retained in adulthood is a kind of pigmentation of the skin.
answered by G R