Which of the following is NOT a sign of an allergic reaction?

Decreased heart rate is not typically associated with an allergic reaction. Allergic reactions, especially those that escalate to anaphylaxis, usually induce a response involving the cardiovascular system that is characterized by increased heart rate (tachycardia) as the body responds to perceived threats. In contrast, the other listed signs—headache and dizziness, rapid labored breathing, and decreased blood pressure—are common indicators of an allergic reaction.

Headaches and dizziness can occur due to inadequate oxygenation or changes in blood pressure frequently seen during an allergic response. Rapid, labored breathing may result from bronchoconstriction and swelling in the airways, common during severe allergic reactions. Decreased blood pressure can occur as a result of vascular dilation and resultant shock, which are part of anaphylactic reactions. Understanding these physiological responses is essential for recognizing and managing allergic reactions effectively.