What physiological response occurs during anaphylaxis?

During anaphylaxis, the body experiences a severe allergic reaction that leads to massive dilation of blood vessels, also known as vasodilation. This vasodilation is primarily caused by the release of histamines and other inflammatory mediators in response to the allergen. As blood vessels dilate, there is an increase in their diameter, which results in a significant reduction in peripheral vascular resistance.

The massive dilation of blood vessels contributes to the hallmark signs of anaphylaxis, such as hypotension (or low blood pressure) and can lead to shock if left untreated. Additionally, this response is part of the body’s attempt to increase blood flow to various tissues, but the rapid and uncontrolled nature of this dilation during anaphylaxis can overwhelm the cardiovascular system.

Understanding this physiological response is crucial for emergency medical personnel, as it directly influences how they manage anaphylaxis, including the administration of epinephrine, which counteracts these effects by causing vasoconstriction and increasing blood pressure.