by Michael Peluso, MS.Ac.

Generally we are taught that sweating at night is a symptom of Yin vacuity and that's about where we leave it. However, there are other recognized patterns in Chinese medicine which may be at play and I thought it worth making a little post about some of these more subtle distinctions to get the juices stirring about pathomechanisms and the concept of mutual engendering.
I have left out any acute causes from external invasions in favor of more chronic, enduring, internally engendered examples as these are the most common in our clinical practice. This is not exhaustive, merely expansionary.

Heart Blood Vacuity:

Typically this patterns results from enduring Spleen Qi vacuity as the Spleen is the latter heaven root of Qi and Blood engenderment. It can also develop from prolonged, heavy bleeding, ofter from profuse menstruation, flooding, etc. As less Blood is available, what is stored in the Liver may create a relative and temporary Yin/Blood vacuity particularly during rest/sleep. This Yin vacuity may lead to Yang hyperactivity and because Yang moves upward and outward the body fluids (such as sweat) are dispersed upward and outward with it.

Spleen Qi Vacuity with Dampness Obstruction:

Poor diet leads to the engenderment of Dampness vis a vis damage to Spleen Qi. Because the Spleen's role in the transformation and transportation of fluids is impaired this dampness and turbidity collects and obstructs the Middle. This creates the perfect storm Li Dong Yuan spoke about whereby the upbearing of the clear and the downbearing of the turbid is inhibited. It is the upbearing of the Clear which allows the Defensive Qi to secure the interstices and prevent the loss of fluids. Additionally because during the night, Yang moves inward, the exterior (interstices) are less secure and more open this accumulation of dampness (fluids) can flow outward more easily.

Damp Heat Depressed and Steaming

Dampness can be either externally contracted or internally engendered. As a Yin evil, it is sticky and stagnant by nature. When encountering the host Qi which is warm, over time it will transform Heat, especially due to obstructing the free coursing of Liver Qi. When dampness obstructs the exterior (interstices) it blocks sweating especially during the day making the inside of the body hot. At night, as Yang retreats inward, the interstices are left less secured and the dampness plus the internal heat move up and out in the form of heat and sweat.

-What you see if you look carefully is that all of these cases are much more likely to happen BEFORE pronounced KD Yin vacuity signs and symptoms arise. These can all easily lead to KD Yin vacuity, dampness traps fluids in a pathological state leading to relative Yin vacuity, Heat can damage Yin, Blood and Body Fluids. Spleen Qi vacuity can lead to Blood vacuity which leads to Yin vacuity.

-In real life, these are part of an evolution, a continuum. Most of these can mutually co-engender (meaning any one can lead to any other one) BUT there is also some directionality too.
Usually the LV/SP are effected first, followed by the KDs after an extended period of time.

• Consider these possibilities next time you have a patient with night sweats. Look for the corroborating signs and symptoms. They may have ALL of these patterns. Be systematic, be rigorously logical. Don't skip steps.