Ultrasonic knife is a cosmetic tool that has emerged in recent years and does not harm the surface skin because ultrasound is not polymerized at the site of skin contact. After repeated ultrasonic knife treatments, the entire SMAS layer of subcutaneous tissue fascial layer can be tightened to achieve the effect of lifting the skin. However, ultrasonic knife surgery is not perfect, its side effects are as follows: 1, if the skin is seriously lacking collagen and hyaluronic acid, it will cause mild scarring, resulting in permanent skin damage, unbalanced skin nutrition, uneven surface, uneven skin tone or even permanent collapse and other side effects; 2, the high temperature during surgery will destroy the moisturizing layer on the surface of the skin, evaporating a large amount of water under the skin, resulting in dry skin performance; 3, after performing ultrasonic knife treatment, the skin will not be damaged. 4.After the ultrasonic knife treatment, the mask cannot be used frequently, otherwise it will affect the recovery of the subcutaneous trauma; 4.Postoperative pigmentation is easy to produce; 5.After the completion of ultrasonic knife, the local skin will show symptoms of swelling, and even redness, pain and numbness, but basically it can heal itself; 6.Pain: the application of anesthetic cream only works on the surface of the skin, and ultrasonic knife treatment works deep in the skin, so during the ultrasonic knife treatment Patients may feel pain in the local skin or under the skin.