Swelling of the face on the second day of tetanus injection is mostly related to inflammatory stimulation and allergic reaction. 1. Inflammatory stimulation, generally speaking, tetanus vaccine rarely causes face swelling directly after the injection, but when the injured part is the head or face, due to the inflammatory stimulation of the wound and tissue laxity, it may lead to the swelling of the injured area, and it is necessary to pay attention to keep the cleanliness around the wound and change the medicine at regular intervals. 2. Allergic reaction, because the vaccine itself is a serum product, some people will have different degrees of allergic reactions after injection, which will lead to an imbalance between the internal and external cellular environment, and then edema of the face or limbs may occur. If the situation is serious, it is recommended to consult a regular hospital in a timely manner, under the guidance of a professional physician to identify the cause of the disease and symptomatic treatment.