What is a common sign of anaphylaxis?

A sudden rash all over the body is a common sign of anaphylaxis because it is a manifestation of the body's severe allergic reaction. Anaphylaxis can stimulate the release of histamines and other chemicals, leading to widespread skin reactions, including hives, swelling, and rashes. This systemic response can occur rapidly after exposure to allergens, such as certain foods, insect stings, or medications.

While the other symptoms listed may occur in various medical conditions, they are not specifically indicative of anaphylaxis. For example, a sudden onset headache could be related to many factors, such as tension or changes in blood pressure, rather than an allergic reaction. Increased thirst could suggest dehydration or other metabolic issues but is not a hallmark of anaphylaxis. Persistent coughing might be linked to respiratory issues but does not directly correlate with the severe, immediate effects of anaphylaxis on the body. Therefore, the presence of a sudden rash all over the body is a crucial indicator of this life-threatening reaction.