"..most of the autonomic vasodilator innervation of the face of normal humans is of sympathetic origin with nerve cell bodies probably located in the superior cervical and stellate ganglia. However, there is also likely to be a parasympathetic vasodilator innervation to specific regions of the facial musculature, particularly that of the lips and forehead. This pathway can be activated by noxious stimulation of the eye or oro-nasal cavity (Drummond 1993, 1994; Kemppainen et al 1994). In some cases, it accompanies eating. This vasodilator response usually is accompanied by sweating, hence the term "gustatory sweating" that sometimes is used to describe this phenomenon (see below). These responses survive sympathetic blockade, and even may be enhanced after chronic loss of sympathetic activity. They probably are due to activation of facial nerve and glossopharyngeal nerve pathways (Drummond 1994), presumably homologous to those described above in rats and cats, via sensory pathways running in the trigeminal nerve."
I was surprised to learn, a number of years ago, that there was no parasympathetic innervation to skin in humans. One of those myths I swallowed pretty much whole way back when, a blithe assumption adopted by soft tissue manual therapy types like myself, was that there was some sort of global parasympathetic response by the human organism to hands-on work, in other words, via skin input. I mean, there had to be, right? People relaxed, and their tummies gurgled; that meant a parasympathetic response, so there must be parasympathetic nerves in the periphery, in the skin, right? Didn't blood vessels dilate? Wasn't dilation "caused" by parasympathetics?
This idea was actively fed as a treatment hypothesis, and/or never properly countered by purveyors of the courses that taught the hands-on work. The same individuals seemed to never carefully check and/or even list their sources. They continued to thereby allow ignorance to slow down the speed of understanding this form of human primate social grooming from a scientific perspective. Only much later did I come to understand, as an individual practitioner, that some kind of global parasympathetic response to direct touch or handling was frankly impossible, that everything out in the body that can be touched, including skin over those forehead and lip muscle bits, is sympathetically innervated, and will react sympathetically.
This only makes sense, given that parasympathetics are mostly about digesting (we don't digest on the outside.. we don't take food in through a surrounding membrane anymore as single cell creatures do). Given our skin is the first layer of sensory protection against exteroception and primarily a radiator for cooling the brain, it especially makes sense given that sympathetics do everything, vasoconstriction or dilation, depending on how they hook up, what transmitters they respond to, and what sort of size they are.
But what about that gurgling? In view of the fact that the brain is not monolithic, that in fact we could even say it's still full of all the creatures we once evolved away from (see "The Beast Within") and knowing that there is no parasympathetic innervation to skin, we could instead conceptualize that some sort of inner highlighting of non-conscious threat tension ensues, and is successfully resolved, right inside the system with which we are engaged. Butler is fond of saying, "Remember, just as you are reading a patient's nervous system, theirs is reading yours." The skin and sensory motor part of the system will see exteroception as a "threat", no matter how kindly it is provided. The human/primate/mammal level probably will not. There will be a battle of sorts within that system, completely invisible from the outside but palpable. The "higher" centers will prevail by regaining the ability to do what they do best, which is inhibit, and peace will be restored to both the body and to the individual who can now more comfortably inhabit that body. If we as practitioners think that we have anything more to do with this process other than catalyze it with handling, we are full of it. The patient's brain does it all, and then gives us some credit (probably ill-deserved much or even most of the time).
Back to the point, about good info on sympathetic/parasympathetic innervation or lack thereof, looking back, I have had more than a few moments of irritation, realizing that it's actually a very deep insult to be treated as if one were nothing but a pair of hands to be trained, no real care taken about what goes into the cognitive "compost bin" attached. Furthermore, I have a lot of irritation that I let my own personal cognitive compost bin be filled with meme garbage of varying kinds, some good and a lot bad. I've done a lot of subsequent composting, finding and tossing out incongruent bits of info; like small toy trucks, they don't break down or blend in, so they are easy to spot and remove. I've turned and aerated the contents on a regular basis, but mental composting is never really finished. It's always a work in progress; eventually however, you can extract something that looks like fertile soil, something that looks like it could sustain mental growth.
More important even than what goes in the bin is how the bin is constructed in the first place - one wants a bin that is rat proof. Instructors who name reliable external sources give one the means with which to reinforce the bin anywhere/everywhere, anytime. I can say without hesitation, don't ever waste your money going to courses where no one names sources, or where the sources are only vague or self-referent. The maintenance of a solid bin is too important in the long run, and developing gentle means by which to handle people in pain is too strategic a goal to permit its continued erosion by poor scholarship.
How does one correct the direction soft tissue work took way back when? One can't - one can only save oneself, share the story, warn others, and demand higher standards in general.