Purgatives (gong xia)

Purgatives are downward draining herbs that expel pathogenic factors by facilitating the passage of the stool. Most purgatives are bitter and cold, like da huang (rhubarb root, Rheum palmatum), and clear constipation due to heat, but another class of moist laxatives, consisting mainly of nuts and seeds, such as huo ma ren (Cannabis sativa), facilitate passage the stool through lubrication.

Their milder action is appropriate for the elderly and debilitated. A final group of harsh cathartics are toxic, inducing pronounced diarrhoea to eliminate excess water, and include herbs like shang lu (poke root, Phytolacca acinosa).