Picosecond countertanning is mainly characterized by localized hyperpigmentation, which makes the skin dark and dull. There are two kinds of cases: normal reactive pigmentation and abnormal pigmentation. 1. The local skin will be stimulated after picosecond laser, which will make the normal melanocyte function active, thus synthesizing more melanin, which will lead to local pigmentation in the short term after precipitation, and this is a normal reaction after treatment, which can be subsided by itself. 2. If due to improper selection of laser machine, laser energy is too high or improper care after laser, it will lead to localized facial skin damage, excessive damage or improper care after treatment will appear similar to anti-black inflammatory pigmentation. When the above phenomenon occurs after picosecond laser, it is considered to be picosecond anti-blackness, and the former will generally subside by itself. If the situation of backward blackness after picosecond laser has not been improved, it is recommended to go to a regular hospital to consult a specialist, and follow the instructions of standardized treatment.