In Traditional Chinese Medicine (TCM), Bai Jiang 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 Bai Jiang Cao is Cold in nature. This means that Bai Jiang Cao typically helps people who have too much 'Heat' in their body. 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 Bai Jiang Cao can help restore a harmonious balance between Yin and Yang.
Bai Jiang Cao also tastes Bitter and 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. Bitter ingredients like Bai Jiang Cao tends to have a cleansing action on the body by clearing Heat, drying Dampness and promoting elimination via urination or bowel movements. On the other hand Pungent ingredients tend 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 Bai Jiang Cao is thought to target the Stomach, the Large intestine and the Liver. In TCM the Stomach is responsible for receiving and ripening ingested food and fluids. It is also tasked with descending the digested elements downwards to the Small Intestine. The Large Intestine on the other hand receives the "impure" parts of the digested food from the Small Intestine, absorbs the remaining fluids and excrete the remainder as feces. The Liver is often referred as the body's "general" because it is in charge of regulating the movements of Qi and the Body Fluids. It also takes a leading role in balancing our emotions.