Tetanus shot, if administering tetanus toxoid, a skin test is required before injection. If the skin test is negative and there is no allergy, then the injection can proceed without stimulating the brain. A small proportion of patients undergoing anti-tetanus treatment might experience some uncomfortable reactions, commonly allergies, fever, and symptoms of vomiting. Generally, these can be alleviated with rest or symptomatic treatment. Only less than 1% of patients may experience seizures or coma, which are very rare reactions. If such reactions occur, it is urgent to go to a formal hospital for symptomatic and supportive treatment. For the vast majority of tetanus shots, if administered in a formal hospital and the patient has a negative skin test, or if given tetanus immunoglobulin, it does not stimulate the brain.