A tongue appearing blue-green is described in the "Tongue Coating Comprehensive Records" as "like the tongue of a water buffalo," caused by stasis and obstruction.

The blue-green tongue is similar to the blue tongue. The "Miraculous Medical Tongue Mirror" states: "Among the five colors, there is blue-green but no blue; blue is light while blue-green is deep, hence blue is easily mistaken for blue-green." The "Guide to Tongue Differentiation" mentions: "Blue is a combination of green and blue-green." However, a blue tongue often indicates cold and stasis, while a blue-green tongue often indicates dampness-heat and liver wind, and is relatively rare. The clinical significance of the two is different. In ancient literature, blue tongue and purple tongue are often discussed together, but according to clinical observations, there are still certain differences in the diseases they indicate, hence they are discussed in separate sections.

bubble_chart Pattern Analysis

1. Cold Congealing and Yang Stagnation︰The main clinical manifestations include a bluish and moist tongue, aversion to cold and curled-up lying posture, reversal cold of limbs, absence of thirst, vomiting, diarrhea, abdominal pain, or diarrhea with undigested food, or bluish discoloration of the hands, feet, nails, and lips, a deep, slow, and weak pulse, or even absence of pulse. This is often caused by cold pathogens directly invading the interior. The *Tongue Coating Comprehensive Records* states: "A bluish tongue... is a sign of cold pathogens directly attacking the liver and kidney, with no case attributable to heat." Cold is a yin pathogen, and when pudendal coldness is excessive internally, yang qi becomes depressed and fails to circulate, leading to stagnation of qi and blood, hence the bluish appearance of the tongue. In cases of external contraction diseases, this often indicates cold pathogens directly attacking the Shaoyin or Jueyin channels. Alternatively, in chronic sexually transmitted diseases, repeated sweating and purgation may damage yang qi, leading to liver and kidney deficiency and decline, with cold arising internally. A bluish tongue signifies impending exhaustion of yang qi. The *Miraculous Medical Tongue Mirror* states: "If Zabing presents this,... it is a sign of true yang decline and exhaustion. In cases that may still be treatable, the tongue may show slight bluishness or faint blue streaks... indicating the visceral qi is not yet completely depleted." The key diagnostic points are: a bluish tongue texture, a slightly moist tongue surface, and symptoms of deficiency-cold in the zang-fu organs (fear of cold, cold limbs, bluish discoloration of the hands, feet, nails, and lips, and a slow pulse). Treatment should focus on heavy formulas to warm yang and dispel cold, such as Cold-Extremities Decoction, Aconite Middle-Regulating Decoction, or Evodia Decoction. The *Guide to Tongue Differentiation* states: "A bluish and slippery tongue coating is a sign of pudendal coldness and should urgently be treated with warming agents like reversal cold of limbs and Evodia. If external symptoms include a bluish face, purple lips, scrotal retraction, reversal cold of limbs, muscle rigidity, and staring eyes, these are critical signs of Jueyin collapse and are incurable." Thus, a bluish tongue warrants serious attention.
2. Static Blood︰The main clinical manifestations include a bluish and dry tongue, dry mouth with a desire to rinse but not drink water, a dark complexion, cyanotic lips, chest fullness, scaly skin, purplish-black bleeding, and a slow, thin, and choppy pulse. Locally, there may be bluish-purple patches, abdominal masses or tumors, and stabbing pain. The primary causes are threefold:
   1. invasion of cold pathogens, zang-fu organs where blood congeals when exposed to cold;
   2. qi deficiency or qi stagnation failing to promote blood circulation, leading to stasis; and
   3. trauma or other causes of bleeding, with extravasated blood remaining in the body.
   The presence of static blood manifests as a bluish tongue, similar to bruising on the skin after trauma. The key diagnostic points are: a bluish tongue texture, slightly dry tongue surface, possibly accompanied by a gray coating, along with other signs of internal static blood obstruction (skin ecchymosis, scaly skin, abdominal masses). The *Guide to Tongue Differentiation* states: "A bluish tongue with dry mouth, a desire to rinse but not drink water, flaccid lips, chest fullness, absence of chills or fever, a slightly large but slow pulse, no abdominal distension, yet the patient complains of fullness—this indicates internal static blood." This serves as a reference for differentiation. Treatment involves not only invigorating blood and resolving stasis but also addressing the root cause of stasis for holistic management.

bubble_chart Documentation

1. "Song of Tongue Diagnosis and Verification": "Purplish macula in the middle of the tongue indicates excessive liver depression. Treatment should focus on dispersing and draining, promoting tranquility, and maintaining a calm and peaceful state, which will lead to the disappearance of the purplish color."
2. "Comprehensive Records of Tongue Coating": "A blue tongue in pregnant women indicates a dead fetus in the uterus. It is advisable to use Stomach-Calming Powder with Mirabilite for purgation."
3. "Method of Tongue Examination in Clinical Practice": "When the tongue appears green, firm, and withered, it indicates excessive pathogenic qi in the liver and gallbladder meridians. The Fire-Purging Liver-Clearing Decoction is recommended (Bupleurum, Skullcap Root, Gardenia, Chinese Angelica, Unprocessed Rehmannia Root, Raw Liquorice Root)." "When the tongue appears green, swollen, and tender, it indicates deficiency of essential qi in the liver and gallbladder meridians. The Water-Nourishing Liver-Clearing Decoction is recommended (Cooked Rehmannia Root, Chinese Yam, Cornus, Moutan Bark, Poria, Alisma, Schisandra Fruit, Angelica Root, Bupleurum, Liquorice Root, White Atractylodes Rhizome)." "When the tongue appears green and dry, it indicates blood deficiency and excessive fire in the liver. Peripatetic Powder with Moutan Bark and Gardenia is recommended." "When the tongue appears green and moist, it indicates qi deficiency in the liver. Angelica Center-Fortifying Decoction without maltose is recommended."