Allergic reactions to tetanus antitoxin are mainly as follows: 1. Most commonly, a rash or swelling or even erythema starts to appear at the injection site, followed by a rash in various parts of the body, accompanied by itching, and sometimes a fever and swelling. 2. There may be symptoms in other parts of the body, such as nausea and vomiting, swelling and pain of joints, and proteinuria may also appear. 3. Symptoms such as unresponsiveness or irritability, chest tightness and sweating, and decreased blood pressure may occur, and in severe cases, coma may occur. 4, some patients will be injected with tetanus antitoxin after a delayed allergic reaction, the length of time varies, may be a week or even two weeks before the appearance, but also need to be alert and other diseases to distinguish. 5, a few people will have a more serious allergic reaction after the injection of tetanus antitoxin, so you need to do a skin test before the injection of tetanus antitoxin, if the skin test is negative, you can directly inject tetanus antitoxin, if the skin test is positive, you can take desensitization injection method, or switch to tetanus immunoglobulin. In short, when the symptoms of allergy appear promptly to seek medical attention, the specific situation to follow medical advice, timely communication, when the injection is completed need to be observed in the hospital for at least 30 minutes, no adverse reactions before leaving the hospital.