Kong Xian Dan (Rheum-Controlling Elixir; also called Miao Ying Wan and Zi Long Wan) kòng xián dān · 控涎丹

Safety. Kong Xian Dan comes from the Sanyin Jiyi Bingzheng Fanglun and is known by two other names as well, Miao Ying Wan and Zi Long Wan. Three ingredients: two of the three drastic hydragogues this library has already recorded under Shi Zao Tang, plus white mustard seed. The classical indication is rheum that has lodged, and the classical literature extends it to knotted swellings along the neck and to pain that travels along the ribs and the back. The word in the formula name is the one that carries the most weight. Xian is the thin, runny part of phlegm, and in the classical usage it covers what would today be separated into several different things: fluid in the pleural or peritoneal cavity, nodules under the skin, and the matted cervical lymph nodes that older texts call scrofula. A formula name that folds all of those into one word is a name from before the distinction existed, and the distinction matters now. Cervical nodes that persist, feel firm, are fixed rather than mobile, enlarge, or come with night sweats, weight loss or fever have to be investigated: tuberculosis, lymphoma, metastatic carcinoma, sarcoidosis and ordinary reactive nodes are all on that list. Tuberculosis of the neck remains common in much of the world, responds to proper treatment, and leaves damage without it. Nothing in a formula name written centuries ago separates these from one another. The two hydragogues are kansui root and Beijing euphorbia root: toxic, violent irritants to the gastrointestinal mucosa, opposed to liquorice root in the classical incompatibility literature, and described at greater length in the entry on Shi Zao Tang. White mustard seed is not in that order of danger but it is not inert. It is a mustard, and its glucosinolates are the reason mustard plasters raise blisters. Topical mustard preparations are documented to cause chemical burns and full-thickness skin injury, including in children treated with plasters left on too long, and deliberate blistering is still part of some seasonal plastering practices. Taking it by mouth and putting it on the skin are different magnitudes, and this library describes neither. What remains of the classical indication is fluid collections and lumps, and both belong to modern diagnosis first. Pleural effusion has a cause that imaging and thoracentesis will usually find. Ascites has a cause, and ascites from cirrhosis carries an additional hazard: spontaneous bacterial peritonitis, in which fever, abdominal pain or a change in mental state in someone known to have ascites is an emergency measured in hours. A lump in the neck has the differential set out above. This entry records the composition of a historical formula. It gives no amounts, no preparation, no instructions, and it makes no claim that the formula does anything for any of these conditions.