Hyperhidrosis

The Neuroanatomy of Sweating

The peripheral nerve innervation of sweat glands is through sympathetic C fibers releasing acetylcholine which particularly binds to the M3 muscarinic receptor to trigger sweat production.  The number of glands depends on an intact peripheral sympathetic innervation, together with average experienced environmental temperature and humidity, particularly during childhood.

Emotional sweating arises from signals emanating from the amygdala, prefrontal cortex, insula and cingulum, then passing along the same routes as for hypothalamic autonomic sweat innervation.  In contrast to temperature-related sweating, emotional sweating leads to vasoconstriction of blood vessels in the dermis, unlike raised temperature which leads to sweating and vasodilation (hence the cold sweat with emotion).  However, the distinction between temperature and emotional sweating is not absolute, with each influencing the other.