Anaphylactic shock occurs due to which of the following?

Anaphylactic shock is a life-threatening allergic reaction that occurs when the immune system overreacts to a particular allergen. In this condition, the body releases a significant amount of histamines and other chemicals in response to the antigen, which can lead to vasodilation—widening of blood vessels—and bronchospasm, where the airways constrict, making breathing difficult.

The correct answer highlights the underlying mechanisms that lead to anaphylactic shock. The combination of vasodilation and bronchospasm results in a rapid drop in blood pressure and restricted airflow to the lungs, which are the hallmark features of this severe allergic response.

The other choices do not comprehensively describe the physiological processes involved in anaphylactic shock. While an increased heart rate can occur as a compensatory mechanism during shock, it is not the cause of anaphylactic shock. Excessive blood loss may lead to shock but is unrelated to the allergic response that defines anaphylaxis. While severe allergic reactions to food can indeed trigger anaphylaxis, this option lacks the specificity of the physiological mechanisms such as vasodilation and bronchospasm which are intrinsic to the condition itself.