Tetanus is caused by the invasion of the body by tetanus bacillus, a type of anaerobic bacterium that generally thrives in anoxic environments or heavily contaminated wounds such as those exposed to polluted soil or rust. Therefore, if the wound is deep, is in an anoxic environment, or is severely contaminated with soil, rust, or is an open fracture with expanded area, explosive injury, gunshot wound, or animal bite, tetanus treatment is required. Tetanus injections include tetanus toxoid, which requires a skin test, and tetanus immunoglobulin, which does not require a skin test, with an injection generally recommended within 24 hours.