 Vasoconstriction, vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of azodilation, the widening of blood vessels. The process is particularly important in staunching hemorrhage and acute blood loss. When blood vessels constrict, the flow of blood is restricted or decreased, thus retaining body heat or increasing vascular resistance. This makes the skin turn paler because less blood reaches the surface, reducing the radiation of heat. On a larger level, vasoconstriction is one mechanism by which the body regulates and maintains mean arterial pressure. Medications causing vasoconstriction, also known as vasoconstrictors, are one type of medicine used to raise blood pressure. Generalized vasoconstriction usually results in an increase in systemic blood pressure, but it may also occur in specific tissues, causing the localized reduction in blood flow. The extent of vasoconstriction may be slight or severe depending on the substance or circumstance. Many basal constrictors also cause pupil dilation. Medications that cause vasoconstriction include bandit histamines, decongestants, and stimulants. Severe vasoconstriction may result in symptoms of intermittent clorification.