Peripheral vasoconstriction is the constriction of peripheral blood vessels. When constriction of blood vessels occurs, the diameter of the blood vessel decreases, causing a decrease in blood flow.
Peripheral blood vessels are those blood vessels which do not supply blood to major organs or skeletal muscles. A good example of the function of peripheral blood vessels is the blood supply to the skin. Peripheral vasoconstriction, and its opposite, vasodilation, are key to the way in which the human body regulates temperature.
When the body needs to reduce heat, as it would after exercise or exposure to high temperatures, it relies on peripheral vasodilation to dissipate heat by routing the heated blood to the skin's surface. When exposed to cold temperatures, the body uses peripheral vasoconstriction to pull blood to the center of the body, keeping it heated, and reducing the dissipation rate of heat.
Peripheral vasoconstriction has a direct effect on blood pressure. The more that blood vessels are constricted, the higher blood pressure rises. The converse is true of blood vessel dilation. Conditions which require the blood pressure to be elevated are treated with drugs, known as vasoconstrictors, that cause peripheral vasoconstriction. There are also a variety of commonly used drugs that cause peripheral vasoconstriction as a side effect, including antihistamines.