Excerpted from Bensky:  Chinese Herbal Medicine Materia Medica, 3rd ed

• Drains heat and purges accumulations:  for high fever, profuse sweating, thirst, constipation, abdominal distention and pain, delirium, yellow tongue coating, and a full pulse.  This presentation is referred to either as Intestinal heat excess or the yang brightness organ-stage of the six stages of disease.*
• Drains fire:  for fire from excess leading to intense fever, sore throat, hot, swollen, and painful eyes, or fire toxin sores due to heat excess obstructing the blood level.  Particularly useful when these problems are accompanied by constipation.*
• Clears heat, transforms dampness, and promotes urination:  for damp-heat leading to such problems as edema, jaundice, painful urinary dribbling, as well as acute, hot dysenteric disorders.*
• Drains heat from the blood:  for blood in the stool either from bleeding hemorrhoids or heat accumulating in the Intestines.  Also for chaotic movement of hot blood that overflows, manifested in vomiting blood or nosebleed accompanied by constipation.  Can be powdered and administered orally for bleeding from the upper digestive tract.  This is an important herb because it can stop bleeding without causing stasis.*
• Invigorates the blood and dispels blood stasis:  for amenorrhea, fixed abdominal masses, or fixed pain due to blood stasis.  Also for blood stasis due to traumatic injury or Intestinal abscess.  This is an important herb for treating both recent and long-term blood stasis as it can both eliminate static blood that is outside the vessels vial the bowels, and clear the heat that often develops from stasis.  It is used both internally and externally.*
• Clears heat and reduces fire toxicity:  used either topically or internally for burns or skin lesions due to heat.*

Da Huang - Rhei Radix et Rhizoma