It usually takes about three months for the black marks left by the laser to disappear gradually. The black marks produced by laser treatment, whether they are caused by the local trauma caused by the high energy emitted by the laser or the black marks caused by the damage to the normal tissues of the skin due to operation error and excessive energy, are in fact post-inflammatory pigmentation, which is related to the reduction of sulfur hydrogen group and the increase of complexinase activity in the skin after inflammation. Later, due to the body’s trauma repair mechanism, the body’s melanin particles gradually metabolized, so that the black marks gradually disappear, this process usually takes about three months. As a common physical therapy in dermatology, laser treatment should fully inform the patient of the possible adverse reactions before operation, and instruct the patient to pay attention to sun protection and pay attention to the rationality and standardization of the operation process, which will not cause possible medical disputes even if the dark marks appear later.