The appearance of red dots on the surface of the skin, which gradually turn black over time, looks very much like a dark pigmented nevus, and requires careful observation of the appearance to determine exactly how they are formed. If the dots are scattered and distributed, more in number, lightly raised when touched by hand and flattened against the skin, and may be accompanied by itching, it is considered to be allergic purpura, which is a bruise formed after allergic factors cause the capillaries to rupture, causing blood to accumulate within the subcutis, and gradually darkens over time, it becomes very much like a black pigmented nevus. The drug rash caused by taking certain special medications can also appear as black dots fixed in the same area. It is necessary to stop using the suspected medications and if necessary, you can choose to use surgical removal for pathological testing to clarify the diagnosis.