Hyaluronic acid, also known as hyaluronic acid, is one of the components of the dermal tissue of the human body and is responsible for storing water and increasing the volume of the skin, making the skin look full, plump and elastic. However, as we age, hyaluronic acid will continue to lose and lose its ability to store water. Hyaluronic acid injections for cosmetic purposes make use of the properties of hyaluronic acid to supplement synthetic hyaluronic acid into the body, which can play a cosmetic role in filling and shaping the skin. Generally, the larger the molecular weight of hyaluronic acid is, the longer it exists in the body, and it is usually completely degraded within 0.5-3 years after surgery. In addition, the maintenance time of hyaluronic acid in the body is also different with different molecular weight. Hyaluronic acid with larger molecular weight is generally used for contouring, such as injecting the bridge of the nose, brow bone or chin, while medium molecular hyaluronic acid can be used to fill in the forehead, apple muscle, temporal area, etc. The maintenance time is about 8-12 months, and the best shape can be maintained within half a year. Smaller molecular weight hyaluronic acid is generally used for injections for forehead lines or tear troughs, and is generally absorbed within six months, with the best form generally maintained for about three months. If you want to maintain a more desirable effect, repeat injections are usually needed in about six months. Candidates can make supplemental injections at the right time according to the situation of absorption, and make regular face-to-face visits or according to daily self-observation in order to maintain the effect for a longer period of time.