Sweating is transformed from body fluid by yangqi and excretes from the sweat pores. Normally sweat functions to regulate yingqi and weiqi and moisten the skin. Under pathological conditions, sweating becomes abnormal due to the invasion of pathogenic factors and imbalance between yin and yang inside the body. Inquiry of sweating can enable one to understand the nature of the pathogenic factors and the conditions of yin and yang inside the body. Inquiry of sweating includes hidrosis and anhidrosis as well as time, region and quantity of sweating.

Anhidrosis
Anhidrosis when there should be sweating is usually caused by exogenous cold or insufficiency of yin blood and body fluid or asthenia of yangqi.
 
Anhidrosis in external syndrome:
This condition is often seen in external sthenia syndrome due to exogenous cold. Since cold tends to stagnate and contract, the muscular interstices become tense and the sweat pores are closed up, preventing sweating from excreting. The usual symptoms are serious aversion to cold, mild fever and floating and tense pulse, etc.

Anhidrosis in internal syndrome:
This condition is usually seen in blood asthenia syndrome and yang asthenia syndrome due to insufficiency of body fluid. If it is accompanied by such symptoms like dry skin, dry mouth, dry feces, it is usually caused by depletion of body fluid due to exhaustion of the sweat source; if it is accompanied by pale complexion and lips, whitish pale tongue, it is usually caused by insufficiency of yin blood and exhaustion of sweat source; if it is accompanied by aversion to cold and cold limbs, it is usually caused by insufficiency of yangqi and hypofunction to transform qi.