I. Common temporary complications after botulinum toxin injection include common short-term complications: pain, edema, petechiae, purpura, short-term sensory loss, short-term post-injection headache, and prolonged migraine (uncommon). For hyperalgesia and purpura, they can be avoided as much as possible by local anesthesia before injection, proper injection technique, and ice packs before and after injection. There are two types of post-injection headache: mild headache (which can be treated with general over-the-counter analgesics), and severe headache (reported rarely and treated with strong analgesics and oral corticosteroids if necessary). To reduce the risk of purpura, patients should be advised to avoid preoperative medications that affect platelet function (non-steroidal anti-inflammatory drugs, aspirin, etc.). II. Serious side effects 1. Interbrow complications Ptosis is one of the most common complications of botulinum toxin injections in the interbrow unit; the cause is thought to be that the levator muscle is paralyzed due to toxin diffusion; it can be improved with adrenergic eye drops (contraction of the mullerian muscle to lift the lid). The best way to avoid the development of ptosis is not to inject patients who have some degree of prior ptosis (whose frontalis muscle is weakened). In addition, vigorous massage or downward massage may also cause ptosis. When the frown line between the eyebrows extends downward as a wrinkled nasal line, the nasal lift upper lip muscle and the upper lip lift muscle should be avoided when treating the wrinkled nasal line to prevent the upper lip from sagging. 2.Forehead and eyebrow complications When treating horizontal forehead wrinkles, the injection point should be located 1-2cm above the orbital rim to avoid lid and eyebrow sagging in order to reduce diffusion. Injection of a small amount of toxin into the descending brow muscle can also prevent brow sagging. Selecting the right patient is key. Injecting the middle frontalis muscle without making a balanced injection to the lateral frontalis muscle may result in an abnormal expression of lateral brow lift. The corrective measure for this is to supplement the injection of a small amount of toxin to the lateral muscles that were not previously injected. 3. Periocular complications Any periocular injection may lead to ecchymosis, diplopia, paralytic lid ectropion or orbicularis oculi prolapse. If diplopia occurs, covering one eye may provide relief. To prevent diplopia, the injection site should be located outside the orbital rim to avoid spreading the toxin into the extraocular muscles. Inadvertent injection into the zygomaticus major or subzygomaticus area may result in cheek and lip ptosis. For orbicularis oculi injections to treat crow’s feet, the injection site should be more than 1 cm above the zygomatic branch incision to prevent midface and lip sagging. In order to avoid midface and lip sagging, when injecting the orbicularis oculi muscle, the range should be limited to 1 cm outside the eye socket or within 1.5 cm of the lateral canthus, avoiding the lower edge of the zygomatic arch. 4.Perioral complications Although most of the facial injections below use fillers, the adjunctive use of botulinum toxin is also very valuable. When treating perioral wrinkles, injection of the orbicularis oris muscle should be conservative. The orbicularis oris can be injected via the upper and lower lips, and the injection should be symmetrical and superficial. Injections should be conservative, symmetrical and superficial. Over-injection of the orbicularis oris muscle may lead to significant side effects such as lip closure, difficulty in eating and brushing teeth; in addition, it may lead to smile asymmetry or speech disorders (difficulty in pronouncing consonants such as B and P) and diminished lip proprioception. Therefore, it is important to declare these potential risks to all patients (especially those who have music, broadcasting, or acting as their profession) before surgery. Atrophy of the orbicularis oris muscle may also lead to secondary flattening of the lip t. In this case, dermal fillers can be injected at the lip margin to correct this. If the injection site is too high from the orbicularis oris muscle, this may result in inversion, ectropion or temporary drooping of the upper lip. Contraction of the descending labial muscle will form wrinkles and cause the mouth to sag permanently with age. In this case, it can be improved by injecting dermal fillers or botulinum toxin at a point no higher than the midpoint between the lip and jaw in order to soften the labial-chin groove. The position of the descending labial muscle needs to be determined by palpation. Injections into the descending labial muscle may result in unilateral paralysis if the point is positioned too close to the mouth. A good approach is to first have the patient bite down on the upper and lower jaws to confirm the location of the descending labial muscle; next, Botox is injected into the lower part of the descending labial muscle on each side. The location of the descending labial muscle injection site; avoiding too close to the mouth Botox injections for the treatment of nasolabial folds are rarely successful and are therefore best avoided. Botulinum toxin treatment of the nasolabial folds may affect oral function and cause difficulty in pronunciation. In most cases, the nasolabial folds should be treated with dermal fillers. 5.Chin and neck complications Botox injection of the chin muscle (lateral to midline of the chin) is commonly used to treat chin depressions. Chin depression is caused by the activity of the chin muscle combined with the lack of collagen and subcutaneous fat in the chin. Injections into the chin muscle may cause depression of the lower lip if the descending lip muscle is accidentally injected. In patients with chin depressions associated with chin muscle hypertrophy, chin injections should be avoided because they are particularly prone to mouth dysfunction. Excessive injections into the chin sulcus may result in impairment of mouth function or lead to an asymmetrical smile. However, injecting the chin muscle in the chin position does significantly soften the contour of the area. After injection, adequate massage should be performed. Botox can also be used to treat broad cervical bands (vertical lines) and horizontal neck lines. Patients with good skin elasticity and little fat deficiency under the chin are suitable to receive injections in the broad cervical band. Since the broad cervical muscle is a superficial muscle, it should never be injected too deeply, otherwise it may lead to swallowing difficulties (life-threatening) or voice change. 6. Systemic complications Botulinum toxin sensitization is a dose-dependent complication: in general, the maximum injectable dose for cosmetic patients is 20-100 U, and the chance of rejection is much smaller than for therapeutic patients (injectable dose up to 300 U).