In Traditional Chinese Medicine (TCM), Yu Xing Cao belongs to the 'Herbs that clear Heat and relieve Toxicity' category. Herbs in this category are used to clear inflammatory and infectious conditions, referred to as 'Internal Heat' in TCM. This is why most of the herbs in this category will have both antibacterial and antiviral properties. In TCM one has too much 'Internal Heat' in their body as a result of a deficiency of 'Yin' (which is Cold in nature, see our explanation on Yin and Yang) or, more commonly, an Excess of Yang (Hot in nature). Herbs that clear Heat and relieve Toxicity treat the latter while, at the same time, removing infectious toxins from the body. As such they tend to be Cold or Neutral in nature.
As suggested by its category Yu Xing Cao is Cool in nature. This means that Yu Xing Cao tends to help people who have too much 'Heat' in their body, although with less effect than a plant that would be Cold in nature. Balance between Yin and Yang is a key health concept in TCM. Those who have too much Heat in their body are said to either have a Yang Excess (because Yang is Hot in nature) or a Yin deficiency (Yin is Cold in Nature). Depending on your condition Yu Xing Cao can help restore a harmonious balance between Yin and Yang.
Yu Xing Cao also tastes Pungent. The so-called 'Five Phases' theory in Chinese Medicine states that the taste of TCM ingredients is a key determinant of their action in the body. Pungent ingredients like Yu Xing Cao tends to promote the circulations of Qi and Body Fluids. That's why for instance someone tends to sweat a lot when they eat spicy/pungent food.
The tastes of ingredients in TCM also determine what Organs and Meridians they target. As such Yu Xing Cao is thought to target the Lung. In addition to performing respiration, the Lungs are thought in TCM to be a key part of the production chain for Qi and the Body Fluids that nourish the body.