Refers to a sensation of the warmth accompanied by erythema, usually over the face, neck, ears, chest and limbs.
It is caused by the basal dilatation and increased cutaneous blood vessel flow.
Vasodilatation is mediated by neurogenic regulation of cutaneous blood vessel smooth muscle or by direct action of histamine, substance P and prostaglandins on endothelial cells.
Histamine acts via H1 and H2 receptors to cause vasodilatation and vascular permeability.
Histamine acts through H3 receptors affecting neurogenic vasodilatation through local neuron-mast-cell feedback loops.
Flushing secondary to neurogenic stimuli is accompanied by sweating, because autonomic innervation of the eccrine sweat glands.
Flushing secondary to vasodilator chemicals is dry i.e. without sweating.