Aromatic herbs have a very special function in transforming Dampness and breaking up the blockage of the Qi. They can penetrate into turbid Dampness because their light but sharp smells are able to separate the clean from the turbid. Meanwhile, their light but exceptional smell can wake up (stimulate) the internal organs that have been covered and confused by Dampness. The aromatic and pungent smells of these herbs can, on the one hand, stimulate the Spleen to transform Dampness and treat the causes of Dampness accumulation; on the other hand, they activate Qi movement so as to accelerate the functions of the involved organs.

In clinical practice, the aromatic herbs are often used to remove Dampness from the Middle Jiao, the Spleen and Stomach. They are also used for eliminating Dampness from the Liver and Gall Bladder as well as from the Heart. Some of them can open the orifices and treat ‘Lock-up syndrome’. They can also be applied topically to treat open wounds or trauma because they are able to transform the pus, dry Dampness, promote the movement of Qi and Blood, reduce swelling, stop pain and promote healing.

Although the functions of aromatic herbs are similar to those of the herbs that regulate the Qi, herbs that eliminate Dampness and herbs that clear Damp-Heat, they have their own specific characteristics and they do not fit easily into any of the herbal categories mentioned above. For this reason in many books they are included within the categories of herbs that aromatically transform Dampness, herbs that clear Summer-Heat, herbs that open the orifices and herbs for external usage.

Herbs that have an aromatic smell are able to transform turbid Dampness in the Middle Jiao and treat the syndrome of Dampness accumulation. This syndrome occurs in certain conditions. First of all, it happens when the Spleen is not able to transform Dampness in situations where there is Excessive-Dampness invasion or deficiency of the Spleen-Qi. Secondly, it can also happen when the Qi movement is disturbed in the Middle Jiao.

In this syndrome, Dampness as well as undigested food, Cold or Heat accumulate in the Middle Jiao and bring about symptoms and signs such as fullness in the chest, distension in the hypochondriac region and abdomen, a poor appetite, a sticky sensation in the mouth, nausea, vomiting, diarrhea or difficult defecation and heaviness of the body. Patients may have a thick, sticky, white or slightly yellow tongue coating and a moderate pulse.

There are many methods and herbs for treating Dampness: some herbs can drain out Dampness by promoting urination, some can dry Dampness directly and some can regulate the Qi to transform Dampness. The aromatic herbs that enter the Spleen and Stomach meridians can penetrate into turbid Dampness, wake up the Spleen which has been covered by Dampness, and stimulate the Spleen-Qi to transform Dampness as well as activating the Qi movement and therefore accelerating the process of transforming Dampness.

These four herbs are aromatic and pungent and are able to expel Wind, Dampness and Summer-Heat, as well as transforming Dampness in the Middle Jiao. They are often used for treating abdominal influenza, acute gastritis and hepatitis accompanied by symptoms and signs such as fever, chills, headache and a heavy sensation in the head, fullness in the chest, gastric and hypochondriac regions, reduced appetite, nausea, vomiting, a thick and white tongue coating and a superficial and moderate pulse.

Of these four herbs, Xiang Ru is the warmest. It is able to induce sweating, disperse Wind and Dampness and release the Exterior. It is especially useful when fever, general pain and heaviness of the body are present but there is no sweating. This herb is also called Summer Ma Huang because it has a similar effect to Ma Huang ( Herba ephedrae) in inducing sweating, but is gentler. Xiang Ru is more suitable for use in the summer, when the pores are not closed so tightly as in winter. It has also the function of transforming Dampness in the Middle Jiao and treating abdominal pain, vomiting, diarrhea and edema, but its action is not as strong as that of the other three herbs.

Huo Xiang is an excellent herb for expelling Wind, Cold and Dampness and can also transform Dampness in the Middle Jiao. Compared with Xiang Ru, its action is stronger in transforming Dampness in the Middle Jiao; compared with Zi Su Ye, it not only expels Wind and Cold, but also disperses Dampness in the superficial layers of the body. This is the most commonly used herb for treating cold and influenza infections and acute gastritis, especially in the summer.