Also known as Semen Brassicae in Latin, it refers to the seed of Brassica alba (L.) Boiss., which is an annual or biennial herb of 30 to 100cm in height. It is spherical, 1 to 1.6mm in diameter, and with deep yellow to brownish yellow testa, or reddish brown in some. Observed under a magnifying glass, the surface presents tiny net texture and clear hilum. Seeds become enlarged after soaked in water for a while, two cotyledons seen after seed coat removed, folded along the main vein, and radicle located between 2 cotyledons. Dried seed is odorless but tastes like oil at first and acrid later. After smashed and wetting, it sends out peculiar pungent smell. By the way, for medicinal purpose, the better one is full grains, uniform size, yellow or reddish brown in color.

CAUSES OF COUGHING UP MUCUS IN TCM
From the perspective of Traditional Chinese Medicine (TCM), simply put it is the result of imbalance of lung and spleen or pathogenic factors. After the assault by pathogens, lung fails to perform the duty of transporting and distributing fluid to the whole body, which in turn is congealed in lung and results in symptoms and signs such as reversed Qi, cough, and wheezing caused by the excessive amounts accumulated inside. According to the nature, it can be classified as four different categories – heat, damp, dry, and cold. There are many herbal remedies available to get rid of cough and mucus, among which Bai Jie Zi is one of the most mentioned.

White mustard seed

HERBAL REMEDY FOR COUGHING UP PHLEGM
Documented in Fang Mai Zheng Zong, Orthodox School of Recipes and Pulse Study, this herb was used for a lump in the abdomen due to wind-damp pathogens, and saliva and sputum congealation. The method is to mix its powder with vinegar and then plaster them on the lump externally, or internally take the pills bonded with Shen Qu (Medicated Leaven);

According to Pu Ji Fang (Prescriptions of Universal Relief), its powder combined with wine treats regurgitation, throwing out food, abnormal rising of Qi, and no desire to move due to weakness;

Jie Zi Jiu Yun Fang, from Sheng Ji Zhong Lu (The Complete Record of Holy Benevolence), is designed for wind-cold in lung and aphonia after typhoid fever. The steps are as follows – grind the seeds into powder, boil them with wine to medium heat, pack them with gauze to iron the neck around, and change after it turns cool;

San Zi Yang Qin Tan, from Han Shi Yi Tong (Han’s Treatise on General Medicine), is aiming to bring relief to coughing up mucus, reversed Qi, and abdominal bloating due to swallowing the phlegm, unconsciously or semiconsciously, instead of coughing it out. The individual herbs in this formula are Bai Jie Zi (White Mustard Seed), Su Zi (Purple Perilla Fruit), and Luo Bo Zi (Carrot Seed).