Hyaluronic acid injections are a safe and effective, minimally invasive cosmetic procedure that is widely used for rejuvenation and contouring. However, with the rapid increase in the number of injection cases, a number of adverse reactions and even serious complications have been widely publicized. Due to the trauma of the injection itself and the occupancy effect of hyaluronic acid in the tissues, local redness, swelling, distension, itching, and bruising are normal reactions to the injection, which usually do not require special treatment and can completely subside in 1-2 weeks. Adverse reactions occur 0-2 d after injection and are mainly manifested as under-correction, over-correction, improper location of filling materials, uneven surface, etc. Preventive measures: one should be familiar with the nature of various hyaluronic acid filler materials and reasonably choose products with appropriate particle size or viscosity; choose appropriate indications, and be cautious in applying to patients with excessively lax skin, or thin skin and poor elasticity. Vascular crisis after injection is the most serious immediate adverse reaction. In recent years, there has been a gradual increase in the number of cases of vascular embolism due to injection, resulting in skin necrosis and even blindness, and therefore, deserves special discussion. Vascular crisis can arise from embolism due to direct injection of hyaluronic acid into the blood vessels or from vascular compression due to overdose of locally injected material. In general, the prerequisites for vascular injury after injection are: (1) an abundant blood supply to the tissue; (2) damage to the parenchymal tissue; and (3) a sharp increase in local pressure. Blunt needles are a safer choice because they do not easily puncture blood vessels. However, blunt needles are not absolutely safe. If there are too many injections and too much local tension, it is difficult for the blood vessels to slide, and even blunt needles may pierce the blood vessels. The effect of local cold compresses is that they can make the blood vessels constrict, and the needle is not easy to enter the blood vessels, thus reducing the possibility of injectables entering the blood vessels. Epinephrine can cause strong local vasoconstriction, which can likewise prevent the needle from piercing the blood vessels, but attention should be paid to contraindications such as hypertension when using it. It is especially important to choose the appropriate injection level. The commonly used injection levels include the middle to deep dermis, subcutaneous tissue, and periosteum; the operator should choose the appropriate injection level according to the anatomical structure of the filling site and the filling effect, avoiding important blood vessels and nerves. Generally abide by the principle of “rather deep than shallow, rather less than more”; massage evenly after injection and brake appropriately, you can choose to physically brake a transparent tape on the surface of the injection site (nasolabial folds), and inject botulinum toxin to reduce muscle activity (forehead lines, frown lines, etc.). Generally speaking, when injecting the tear trough and submental folds, the level should be on the periosteum of the infraorbital rim; the orbito-zygomatic area (commonly known as “apple muscle”) should be injected on the periosteum to avoid the infraorbital artery; when injecting the nasolabial folds, the periosteum should be chosen above the level of the nasal spine and below the level of the nasal spine should be in the superficial subcutaneous layer to avoid the facial artery; the chin can be injected on the periosteum and the subcutaneous fat layer to create a three-dimensional appearance. Injections in the forehead should be made on the periosteum or in the superficial subcutaneous layer to avoid the superficial temporal artery and the middle temporal vein; injections in the nose should be made on the periosteum to avoid damaging the blood vessels in the dorsal nasal fascia. Before each injection, the empty needle must be drawn back to determine whether it is outside the blood vessels. The amount of injection should not be too large at one time, but should be injected several times in small amounts; the injection force should not be too large, and should be pushed as gently as possible. When the patient suddenly develops radioactive pain, he should be highly alert to whether there is vascular injury; if there is more bleeding, he should also suspect whether there is vascular injury; at this time, the injection site should be changed and repeated pushing at the same point should be avoided. The typical manifestation of vascular embolism is pain and skin color change, which may appear as pale, florid or blue-purple skin. Therefore, the physician should closely observe the skin changes during the injection to detect the possible vascular embolism in time, and once it occurs, local hot compresses should be applied to dilate the blood vessels, and steroid hormones, low molecular heparin sodium and aspirin drugs, as well as salvia and poppy bases to activate the blood. If hyaluronan is clearly caused, hyaluronidase should be injected immediately at the injection site, and antibiotics and antivirals should be used to prevent infection if necessary. Once signs of ophthalmic artery embolism appear or are suspected, a consultation with an ophthalmologist should be sought for timely detection and early management. In conclusion, although the probability of vascular complications is low, if they do occur, the consequences are usually more serious, so they should be taken more seriously. There are many types and brands of injectable materials available for clinical use, each with its own relatively specific risk of complications, and injection requirements are often different. Before each injection, the anatomical structure of the injection site should be clarified; a detailed medical history should be taken to exclude contraindications and minimize risks; choosing the appropriate injection material, mastering the correct injection technique, and making adequate preparation can avoid the majority of complications.