Anaphylaxis is a severe and potentially life-threatening allergic reaction. There are several synonyms for the word anaphylaxis, including anaphylactic shock, anaphylactoid reaction, and systemic allergic reaction. Anaphylactic shock is the most commonly used synonym and refers to the condition where a person's blood pressure drops suddenly, and their airways constrict, making breathing difficult. The term anaphylactoid reaction is used to describe a similar reaction, but it occurs without the presence of an allergen. The term systemic allergic reaction is also used interchangeably with anaphylaxis and refers to a reaction that affects the entire body. Recognizing the signs and symptoms of anaphylaxis is important to seek immediate medical attention to avoid complications.