The accelerated pace of life, changes in working methods, environmental pollution, and the ageing of the “culprit” will cause our eyes, lips, forehead and other parts of the body, slowly covered with various wrinkles. With the advancement of technology, cosmetic surgery is gradually developing in the direction of minimally invasive and non-invasive with the help of advanced surgical instruments to ensure safety and efficacy, such as the ultrasonic knife. Ultrasonic knife has always been the highlight of non-invasive, fast results, tightening contours, smoothing and fading wrinkles, and is worshipped by many beauty seekers as a god. However, many sensible beauty seekers will be distracted to consider the issue of “ultrasonic knife safety” while they are eager to try it. In fact, compared to traditional surgery, which is highly traumatic, risky and has a long recovery period, ultrasonic knife greatly improves the safety of surgery and reduces the occurrence of post-operative complications or side effects, which has absolute advantages over traditional surgery. However, it is always a technology that uses focused ultrasound to treat deep in the skin. Once the treatment process is improperly operated by technicians or the quality of the machine is not up to standard, serious damage is likely to occur. Even if there is no serious damage, some minor side effects cannot be easily ignored. For example, after the procedure, the patient’s treatment area will generally have pain, redness, edema, bruising, etc., but most of them are self-limiting. Very few of them will also have local pigmentation changes, mainly because ultrasonic knife only works on the set target depth, the operation preserves the superficial skin barrier and is not absorbed by the chromogenic mass. In addition, pain is one of the most frequent side effects after ultrasonic knife surgery. Almost all of the above are relatively mild or can be recovered quickly, but not everyone is that lucky. Some candidates may experience ulcers, erosions, blisters, and acne outbreaks, which are mostly related to improper operation. Firstly, it may be that the operator did not properly fit the instrument to the skin, causing superficial damage; secondly, it may be that the proper distance was not spaced out causing pulse buildup. In the investigation related to post-operative complications of ultrasonic knife, there were 5 cases reported about more serious complications after ultrasonic knife treatment, 2 of which were chronic ulcers and tissue atrophy requiring follow-up treatment, and the other 3 cases were redness, blisters, and superficial injuries, all of which improved after about 9 weeks with no sequelae. This also shows that professional operators are the key to avoid serious complications or side effects. So what can be done if unfortunately side effects occur? The first is pain, as the most common side effect after ultrasonic knife surgery, most candidates can take preventive measures, such as oral painkillers, oral sedatives, topical application of creams containing lidocaine and intramuscular injection of pethidine. However, it has been empirically concluded that patients with pain ratings of 5-6, and up to 7-8 in some bony augmentations, still had pain prevention and pain relief by taking routine pain relief measures prior to treatment. in this regard, it has been suggested that the use of nerve block anesthesia can significantly reduce patients’ pain ratings with no specific side effects, but the details are yet to be proven. Other minor side effects, such as slight redness and edema, usually recover within a few hours, and can be avoided by avoiding hot water without special treatment. It is also important to note that for at least 1 week after the treatment, do not exfoliate the treated area and use soothing, non-irritating creams or products. If you need to apply makeup on a daily basis, mineral makeup is preferred. If you need to go out in the sun, use a sunscreen with SPF 30 or above to avoid sun damage. There is nothing wrong with the love of beauty, and there is nothing wrong with the act of seeking beauty, but if you do not choose a good institution, thus leading to some irreversible damage, it will make these acts that are not wrong, become wrong. Therefore, medical beauty is risky and needs to be chosen carefully. References [1][1] Zhou Luqi,Ma Gang,Lin Xiaoxi. The application of ultrasonic knife in minimally invasive aesthetics [J]. Tissue Engineering and Reconstructive Surgery,2021,17(01):86-89. [2]Xiong Rui,Chen Lijun. Facial care techniques [M]. Wuhan:Huazhong University of Science and Technology Press,2017,103-105.