Anaphylactic shock can strike a patient at any time or place. It is sudden allergic response to an environmental situation, insect venom or medically-prescribed drug. Although some members of the public may present in the Accident and Emergency department with life-threatening symptoms, the situation is often most serious when a drug has been given. The mechanism of anaphylactic shock is discussed in this article as is the first line treatment. The immune system and the character of immunoglobulins are highlighted, and the role of the nurse in an emergency situation is given consideration. Legal implications of any action taken are looked at from the standpoint of litigation.