At present, the Q-switched series of lasers (including Q-switched frequency doubling Nd:YAG laser, Q-switched ruby laser and Q-switched emerald laser) and intense pulsed light (IPL) are more mature for the treatment of freckles. The former is based on the theory of “selective photothermolysis”, using the appropriate laser energy to burst the pigment particles, while the burst pigment particles are absorbed by macrophages and metabolized by the lymphatic system. The intense pulsed light can easily remove the melanin particles in the basal layer, and its cooling system can reduce the temperature of the surrounding tissues and thus reduce the degree of damage, and after the procedure, there is only temporary erythema and a slight burning sensation, and most of the lesions are temporarily colored and healed after about 1 week. It is important to note that the chance of inflammatory hyperpigmentation (PIH) after treatment with different wavelengths of Q-switched lasers is about 10-25% in the Asian yellow population. Therefore, to prevent hyperpigmentation and a large number of postoperative recurrences, patients should avoid UV exposure as much as possible and topical application of highly effective sunscreen products (physical or chemical with SPF 30+) is necessary. If necessary, oral vitamin C and vitamin E should be taken. In 2015, the Chinese medical aesthetics industry also started the era of the most cash-intensive picosecond laser treatment for pigmentation diseases, and we will introduce this “extraordinary” laser spot removal technology separately below. Picosecond laser – the most advanced laser spot treatment technology Picosecond laser technology is the most advanced laser technology, which is used to whiten and remove spots with its ultra-short pulse width, and was approved by the FDA in 2012 for the treatment of skin diseases. What pigmentation can be removed by picosecond laser? Picosecond laser can solve almost all kinds of pigment spots, such as freckles, age spots, coffee spots, cheek brown spots, nevus of Ota, sun spots, eyebrow tattoos, etc. It is the gold standard for the treatment of refractory tattoos. Moreover, picosecond laser has gained a better prospect in the treatment of melasma. What are the advantages of picosecond? According to the “principle of selective photothermolysis” mentioned above, the shorter the action time of laser, the less the laser energy absorbed in the target tissue will spread to the surrounding tissues, and it will be more concentrated in the target target to be treated, so that the melanin can be removed at the same time without hurting the surrounding normal tissues. The shorter the time, the less likely it is for the laser energy to spread to the surrounding tissues. The body’s immune system will swallow these broken pigment particles and eliminate them from the body, so it is very safe. The pulse width of picosecond laser is only one thousandth of that of traditional Q-switched nanosecond laser, under this ultra-short pulse width, the light energy can not be converted into heat energy, and almost no photothermal effect is produced, and the energy is absorbed by the target melanin particles and then blasted into fragments by the photomechanical effect. The number of treatments can be shortened from 10 to 2-3 times, and the risk of stimulating melanin proliferation (anti-darkness) is also being reduced. In conclusion, picosecond laser is more thorough in breaking down pigment particles, with better efficacy, less treatment times and less adverse reactions. Compared with other treatment methods for spot removal, the treatment is more thorough, the recurrence rate is very low, and the probability of re-blackening is effectively reduced. 2.Two birds with one stone – “spot removal + skin rejuvenation” The fractional mode of high efficiency picosecond pulse width laser can also produce small shock waves in the skin, which can start the skin’s own repair mechanism and make the skin produce new collagen for whitening and skin rejuvenation. “killing two birds with one stone”!