In Traditional Chinese Medicine (TCM), Dan Zhu Ye belongs to the 'Herbs that clear Heat and purge Fire and/or clear Summer Heat' 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 purge Fire treat the latter and as such tend to be Cold or Neutral in nature.
As suggested by its category Dan Zhu Ye is Cold in nature. This means that Dan Zhu Ye 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 Dan Zhu Ye can help restore a harmonious balance between Yin and Yang.
Dan Zhu Ye also tastes Sweet. 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. Sweet ingredients like Dan Zhu Ye tends to slow down acute reactions and detoxify the body. They also have a tonic effect because they replenish Qi and Blood.
The tastes of ingredients in TCM also determine what Organs and Meridians they target. As such Dan Zhu Ye is thought to target the Heart, the Small intestine and the Stomach. In addition to regulating Blood flow, in TCM the Heart is believed to be the store of the 'Mind' which basically refers to someone's vitality. Like the Stomach, the Small Intestine has a digestive role, extracting the "pure" part of what we injest to the Spleen and the "impure" down to the Large Intestine. 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.