Which of the following symptoms is considered a systemic symptom of anaphylaxis?

Anaphylaxis is a severe and potentially life-threatening allergic reaction that can involve multiple body systems. It is characterized by a rapid onset of symptoms. While some symptoms of anaphylaxis are classified as local, systemic symptoms refer to those affecting the whole body and can indicate a more severe reaction.

Diarrhea and vomiting are considered systemic symptoms during anaphylaxis because they demonstrate involvement of the gastrointestinal tract, which can occur due to the release of histamines and other chemicals into the bloodstream. This release leads to vascular permeability changes and gastrointestinal disturbances. During an anaphylactic reaction, these symptoms typically appear alongside more classical signs such as difficulty in breathing, hives, or swelling, indicating a serious systemic response.

In contrast, fever, myalgia, and headache are not typically direct indicators of anaphylaxis. Fever is often associated with infections or inflammatory processes, myalgia refers to muscle pain and might be due to a variety of other conditions, and headache can have numerous non-allergic causes. Therefore, among the options provided, diarrhea and vomiting distinctly align with the systemic manifestations expected during anaphylaxis.