What is a common symptom of a severe allergic reaction?

Swelling of the face and throat is indeed a common symptom of a severe allergic reaction, also known as anaphylaxis. This condition occurs when the immune system overreacts to a substance, which can lead to increased vascular permeability and swelling in various parts of the body. Particularly, angioedema, which is swelling beneath the skin, often affects the face, lips, tongue, and throat, posing a significant risk as it can obstruct airways and hinder breathing. Recognizing this symptom is critical for immediate action, such as administering epinephrine, as timely treatment can be lifesaving.

While the other symptoms listed can occur in various situations—headaches can arise from stress or dehydration, stomach cramps frequently come from dietary issues, and a rapid heartbeat can be associated with anxiety or other health conditions—they are not specific indicators of a severe allergic reaction. The presence of swelling in vital areas is a more definitive and urgent sign requiring prompt medical intervention.