What is typically a sign of severe allergic reaction?

Shortness of breath is a key indicator of a severe allergic reaction, also known as an anaphylactic reaction. This symptom occurs when the body's immune system overreacts to an allergen, leading to swelling in the airways, inflammation, and tightening of the muscles around the bronchi. As a result, oxygen flow is restricted, causing difficulty in breathing. This can escalate quickly and may require immediate medical intervention, such as epinephrine administration, to reverse the serious symptoms, including respiratory distress.

Other symptoms of severe allergic reactions can include hives, swelling of the face or throat, and a rapid or weak pulse. In contrast, symptoms like a headache, stomach ache, or fatigue may occur in a variety of conditions and are not specific indicators of a severe allergic reaction. While they can be distressing, such symptoms do not typically signify the immediate life-threatening nature of conditions like shortness of breath in the context of anaphylaxis.