There are people who rarely sweat. Not sweating means either that they have energy to produce heat, but are weak to diffuse it, or that the energy to produce heat itself is weak.
Those who are weak to diffuse heat tend to be yang excess, and the skin is liable to get red and rough, because the heat stays inside of the body. On the other hand, for those who are weak to produce heat, their bodies have coldness, so for women, they have difficulty to get pregnant.
When they receive acupuncture treatments, their bodies gets warmer and start sweating.
*This article is translated from "Yamai hitokuchi Memo" written by Shoji Kobayashi, 2005.