Freckles may rebound after a picosecond. There is a clear correlation between freckles and genetics and sun exposure, so rebound may occur after a picosecond if strict attention is not paid to sun protection or proper care is not taken, for example. Picosecond, or picosecond laser, is a type of cosmetic laser. The duration of the laser it emits is measured in picoseconds. Picosecond laser acts on pigments, capillaries, etc. in the skin at a faster speed and with more powerful energy, while stimulating the skin and speeding up the metabolism. It also promotes the skin to produce collagen fibers, etc., which plays a role in whitening and lightening spots. After picosecond laser, you must pay attention to sun protection. You can also apply a soothing and moisturizing mask externally. Usually 3 times for a course of treatment, each time to do picosecond interval is preferably more than one month. However, it should be noted that photosensitivity, pregnant women and other people are prohibited. It is recommended that patients go to a regular hospital, operated by a professional physician.