Lidocaine is a common local anesthetic used in pain medicine and plays an important role in various nerve blocks and pain interventions. Allergic reactions caused by the application of local anesthetics are extremely rare, but as a pain physician who often deals with lidocaine, we should pay attention to the allergic reactions caused by lidocaine. 1, lidocaine caused by allergic reactions is very rare because it is an amide local anesthetic, non-protein substances, itself can not be sensitized, but sometimes can be used as a semi-antigen, combined with protein or polysaccharide to form an antigen causing allergic reactions. There are three types of drug reactions to lidocaine: (1) overdose. (2) Hypotolerance. (3) Allergic reactions. The allergic reaction of lidocaine is similar to poisoning reaction, but the attack is more acute and accompanied by allergic-like signs, which can be rapid or slow onset, mainly manifested as central nervous system, cardiovascular symptoms and respiratory arrest. 2.Lidocaine dosage for adults (1) Sacral block for labor analgesia, the dosage is limited to 200mg (1.0%); for surgical pain relief, the dosage can be increased to 200-250mg (1.0-1.5%) as appropriate. (2) Epidural block, thoracolumbar segment, 250-300mg (1.5-2.0%). (3) Infiltration local anesthesia or sedation regional block, 50-200 mg (0.25-0.5%). (4) Peripheral nerve block, brachial plexus (unilateral), 250-300 mg (1.5%); dental, 20-100 mg (2.0%); intercostal nerve (each branch), 30 mg (1.0%); paracervical infiltration, 100 mg (0.5-1.0%) on each of the right and left sides ); paravertebral spinal nerve block (each branch), 20-50 mg (1.0%); pubic nerve, 100 mg (0.5-1.0%) on each of the right and left sides. (5) Sympathetic ganglion block, cervical stellate nerve 50mg (1.0%), lumbar 50-100mg (1.0%). (6) Limit once, generally do not exceed 200mg (4.0mg/kg), the dosage of epinephrine added to the drug solution can be increased to 200-250mg (6.0mg/kg), the maximum amount of 300 – 400mg in 1 hour. static regional block, extreme amount 4mg/kg, therapeutic drug for static injection, the first initial amount of 1mg/kg, extreme amount 4mg/kg, adult sedation limited to 1mg per minute. Repeatedly administered several times, the interval between them should not be shorter than 60 minutes. 3.Comparison of clinically used local anesthetics At present, procaine, bupivacaine, lidocaine and bupivacaine are most commonly used in domestic clinics. Procaine is generally used for the first time to skin test, single application of poor anesthesia, the need to add epinephrine, hypertension and heart disease are used with caution. Bupivacaine is mostly used for superficial anesthesia, while lidocaine has been promoted in clinical use since 1954 and is now widely used in intralesional anesthesia as well as local anesthesia and infiltration anesthesia in various areas. The action characteristics of lidocaine: (1) When used for infiltration or block anesthesia, the local diffusion range of the drug is wide. (2) The local anesthetic properties of the degradation products of the amine group after dehydrocarbonization are limited and the toxicity is increased. Allergic reactions are rare. (3) It can cross the placental barrier and bind to fetal proteins, which is more than that of adults. (4) The action of the central nervous system, visible drowsiness and drowsiness, followed by convulsions, and quickly into syncope and deficiency. (5) There are individual differences, and a small amount should be used first. 4.How to determine lidocaine allergy If the patient suddenly appears the following symptoms after the drug: (1) Respiratory symptoms caused by laryngeal and bronchial edema and spasm: chest tightness, shortness of breath. Difficulty in breathing. Asphyxia, purple chancre. (2)Circulatory symptoms: pale face, cold sweat, weak pulse, decreased blood pressure. (3) Loss of consciousness, incontinence, fainting, coma, the occurrence of anaphylaxis should be considered. 5, attention to the problem Lidocaine central nervous system toxic reactions are serious, lidocaine cardiovascular toxicity concentration and central neurotoxicity concentration between the existence of a wide range, cardiac toxicity occurs mostly after the central neurotoxicity, so it should not be ignored. The systemic adverse reactions of lidocaine can be life-threatening in serious cases, and should be resuscitated in a timely manner once they occur. (2) For patients with convulsions who also have hypotension and respiratory arrest, any barbiturates should not be applied or used with caution, such patients can be used Valium. (3) To the central nervous system toxic reactions, patients with respiratory arrest or respiratory depression should do assisted breathing, such as breathing does not resume should do endotracheal intubation, improve ventilation, correct oxygenation. (4) Angioedema patients with vocal edema, which cannot be relieved by resuscitation and severe asphyxia must be immediately tracheotomized. 6. First aid measures (1) Treatment must be temporarily terminated. Call for help. Call 120 emergency number. Immediately make the patient lie flat, loosen the neck collar, make the airway open, stimulate breathing with ammonia, press the human center, and quickly administer oxygen. (2) Measure the patient’s blood pressure, respiration, pulse and body temperature. Isoprostanes 25mg intramuscularly, 5% glucose 200ml plus dexamethasone 5mg sedation. In critically ill patients, slow injection of 2% thiopental sodium 50mg intravenously, 5% glucose 200mg plus dormantine 250mg intravenously. (3) Use of desensitizing drugs such as injection of fenagin (isoprostanes) 25 mg, as well as the use of other methods of symptomatic treatment. 7. Prevention (1) Ask the patient if there is any history of allergy to the drug and if there is any organic lesion in the body before using the drug. Lidocaine currently does not require skin testing, individual patients with a history of allergy to commonly used drugs should also be skin tested. (2) prevent the injection of lidocaine into the blood vessels when local anesthesia, must be carefully aspirated with or without re-blooding, the literature reports a small amount of lidocaine accidentally injected into the vein, there is a risk of cardiac arrest. (3) The department must be equipped with an emergency drug kit, rescue drugs must be sufficient, and the expiration date of drugs must be checked regularly. (4) Equipped with a full set of oxygen equipment, regular inspection and replacement.