Galvanic Skin Response
It is not disputed that small non-random electrical fluctuations are measurable on the skin of a human. This is an element of polygraph testing. Wilhelm Reich investigated this and wrote a slim book about it. A fundamental understanding is that these fluctuations are much more variable over certain areas. These areas were already known as erogenous zones because of their role in sexuality, but it could be fair to call them human contact zones as well.
Erogenous is not the same as erotic. The universal erogenous zones are: the tongue, the lips, earlobes, palms, nipples, anal mucosa, vaginal mucosa, and penis. Many would classify the eyes as erogenous but they are not testable for galvanic skin response. In some the forehead is erogenous. Potentially, a woman's 'throat' (upper-middle anterior of torso with front of neck) is erogenous--that is why even with very conservative dress, a woman's throat is often exposed by the neckline, and necklaces are worn. This aspect of galvanic variability is very different from sensitivity in the usual sense, although there can be overlap as with the lips.
Electrical current changes induced by physical contact in erogenous areas were associated with pleasure, anxiety, or annoyance. The difference in the response was not solely based on the mechanical nature of the physical contact but also the 'readiness' of the stimulated subject. This is consistent with Reich's sex-economic concepts. A raised charge was identified with pleasureable sensation usually and also itch. This explains the use of the term 'itch' to denote 'desire' in folk sayings. Light friction or tickling of an area increased charge, and pressure decreased it. Hypersensitivity to touch is experienced by some people with friction (stroking), and this possibly denotes an inability to tolerate the charge at the surface. Usually in these cases, pressure is welcomed. It is important to note, that Reich did not think these millivolt electrical changes were the main biological effect, but rather just indirect evidence of it.