Vasoconstriction occurs when systemic medications or cold temperatures cause the blood vessels to become narrow or constricted. The flow of blood is restricted, a reaction that can be both helpful and that, in turn, may ultimately create more serious health problems.
Benefits include a relief of sinus pressure and the temporary conservation of bodyheat. In prolonged cases it may cause headache, whitening of the skin, etc. Medications known to create vasoconstriction include decongestants, antihistamines and analgesics.