Blushing is the reddening of a person's face due to psychological reasons. It is normally involuntary and triggered by emotional stress associated with passion, embarrassment, shyness, fear, anger, or romantic stimulation.
Severe blushing is common in people who have social anxiety in which the person experiences extreme and persistent anxiety in social and performance situations.
Blushing is generally distinguished, despite a close physiological relation, from flushing, which is more intensive and extends over more of the body, and seldom has a mental source. Idiopathic craniofacial erythema is a medical condition where a person blushes strongly with little or no provocation. People who have social phobia are particularly prone to idiopathic craniofacial erythema.
A blush is a reddening of the cheeks and forehead brought about by increased capillary blood flow in the skin. It can also extend to the ears, neck and upper chest, an area termed the 'blush region'.
There is evidence that the blushing region is anatomically different in structure. The facial skin, for example, has more capillary loops per unit area and generally more vessels per unit volume than other skin areas. In addition, blood vessels of the cheek are wider in diameter, are nearer the surface, and visibility is less diminished by tissue fluid. These specific characteristics of the architecture of the facial vessels led Wilkin in an overview of possible causes of facial flushing to the following conclusion: "[...] increased capacity and greater visibility can account for the limited distribution of flushing".
Evidence for special vasodilation mechanisms was reported by Mellander and his colleagues (Mellander, Andersson, Afzelius, & Hellstrand. 1982). They studied buccal segments of the human facial veins in vitro. Unlike veins from other areas of the skin, facial veins responded with an active myogenic contraction to passive stretch and were therefore able to develop an intrinsic basal tone. Additionally Mellander et al.