Yi Huang Tang (易黄汤), known in English as Change the Yellow Decoction, is a classical TCM formula by Fu Qing-zhu for treating damp-heat in the lower jiao causing abnormal vaginal discharge (leukorrhea). It is particularly indicated for yellow, thick, sticky, and foul-smelling vaginal discharge, often accompanied by vulvar itching and lower abdominal discomfort. In modern clinical practice, Yi Huang Tang is widely used for gynecological damp-heat patterns with yellow leukorrhea, especially when there is underlying Spleen deficiency. By clearing damp-heat, tonifying the Spleen, and astringing discharge, it effectively resolves the pathogenic damp-heat while addressing the root deficiency that allows it to persist.

I. Origins and History

1. Source of Yi Huang Tang

Yi Huang Tang originates from the Fu Qingzhu Nuke (Fu Qingzhu's Gynaecology), authored by the celebrated Qing dynasty physician Fu Shan. Fu Shan, courtesy name Qingzhu, was a legendary figure among the great physicians of ancient China. Not only was he exceptionally skilled in medicine, he also possessed noble medical ethics, devoting his life to medical research and practice and leaving behind numerous valuable medical writings — the Fu Qingzhu Nuke being one of his classical works. This text offers distinctive and profound insights into the diagnosis and treatment of gynaecological conditions, and Yi Huang Tang, as one of its important formulas, has consistently been valued and applied by physicians of later generations.

2. Historical Evolution and Transmission

Yi Huang Tang is a classical formula for treating yellow vaginal discharge and yellow-coloured vaginal discharge, possessing the actions of clearing heat and resolving toxicity, clearing heat and dispelling dampness, clearing heat and drying dampness, astringing and consolidating to stop vaginal discharge, tonifying ren-vessel deficiency, clearing kidney fire flaring, disinhibiting water and percolating dampness, and tonifying with astriction. It is primarily indicated for sticky, viscous vaginal discharge, vaginitis, cervical erosion, and chronic pelvic inflammatory disease caused by downward pouring of damp-heat. The formula is often combined with a strong tea infusion, taken as a water decoction, and produces good results for the pattern of spleen deficiency with damp-heat.

Since the emergence of Yi Huang Tang, it has undergone several centuries of transmission and development. Physicians across the generations have continuously verified its therapeutic effect through clinical practice, and it has become one of the commonly used formulas within Chinese medicine gynaecology for treating vaginal discharge disorders and related conditions, holding an important place within the developmental history of Chinese medicine formula studies.

II. Herb Composition (Sovereign, Minister, Assistant, Envoy)

1. Chief Herb — Shanyao (Dioscorea Rhizome)

Shanyao is sweet in flavour and neutral in nature, entering the Spleen, Lung, and Kidney channels. In Yi Huang Tang, Shanyao performs the key role of strengthening the spleen and tonifying the kidneys. It can tonify spleen qi, ensuring normal spleen-stomach transforming and transporting function and a source for qi-blood transformation and generation; it can also tonify the kidneys and consolidate essence, producing excellent tonifying benefit for kidney qi depletion. Its texture is moist and nourishing, neither dry nor greasy, capable of both tonifying the prenatal kidneys and nourishing the postnatal spleen, making it the foremost herb for supporting the righteous and consolidating the root. It occupies the core position within the formula, hence serving as the chief herb.

2. Deputy Herb — Qianshi (Euryale Seed)

Qianshi is neutral in nature, sweet and astringent in flavour, entering the Spleen and Kidney channels. It has the actions of boosting the kidneys and consolidating essence, strengthening the spleen and stopping diarrhoea, and eliminating dampness to stop vaginal discharge. Combined with Shanyao, it reinforces the action of tonifying the kidneys, strengthening the spleen, and consolidating and stopping vaginal discharge. Qianshi's astringing and consolidating nature helps to constrain the slippage pattern of the lower burner, producing excellent therapeutic effects for symptoms such as excessive, thin vaginal discharge, assisting Shanyao in exerting the primary therapeutic action — hence serving as the deputy herb.

3. Assistant Herb — Huangbai (Phellodendron Bark)

Huangbai is bitter in flavour and cold in nature, entering the Kidney, Bladder, and Large Intestine channels. It can clear heat, dry dampness, drain fire, and resolve toxicity. In Yi Huang Tang, Huangbai primarily clears and disinhibits lower-burner damp-heat. It can eliminate the damp-heat pathogen within the body, preventing damp-heat from accumulating and binding in the lower burner and aggravating the condition. Simultaneously, Huangbai's bitter-cold nature also restrains the warm-tonifying nature of Shanyao and Qianshi, allowing the entire formula to tonify without stagnation and clear heat without being overly cold — performing a mutually reinforcing role, hence serving as the assistant herb.

4. Envoy Herb — Cheqianzi (Plantain Seed)

Cheqianzi is sweet in flavour and cold in nature, entering the Liver, Kidney, Lung, and Small Intestine channels. It has the actions of clearing heat, promoting urination, and unblocking painful strangury, percolating dampness and stopping diarrhoea, brightening the eyes, and dispelling phlegm. In Yi Huang Tang, Cheqianzi primarily exerts a heat-clearing and dampness-disinhibiting action, guiding the damp-heat pathogen to be expelled via urination. It can reinforce Huangbai's effect of clearing and disinhibiting lower-burner damp-heat, while also harmonising all the herbs, allowing the medicinal force to better act upon the site of disease — hence serving as the envoy herb.

III. Pathomechanism, Actions, and Indications

1. Pathomechanism Analysis

The pathomechanism targeted by Yi Huang Tang is primarily dual spleen-kidney depletion, with downward pouring of damp-heat. The spleen governs the transformation and transport of water-dampness, and the kidneys govern storage and consolidation. When the spleen and kidneys are weak, transformation and transport fail in their duty, and storage and consolidation lose their authority; water-dampness is internally generated, and the dampness pathogen, accumulated over time, transforms into heat. The damp-heat pathogen then pours downward into the lower burner, giving rise to vaginal discharge disorders and related conditions.

2. Actions

Yi Huang Tang has the actions of tonifying the spleen and boosting the kidneys, clearing heat and dispelling dampness, and astringing and consolidating to stop vaginal discharge. Through tonifying spleen-kidney depletion, the body's righteous qi is reinforced, improving its capacity to resist pathogenic factors; through clearing and disinhibiting lower-burner damp-heat, the causative factor of disease is eliminated; through astringing and consolidating to stop vaginal discharge, the abnormal vaginal discharge symptoms are improved — thereby achieving the goal of treating both root and manifestation.

3. Indications

Yi Huang Tang is primarily used to treat vaginal discharge disorders caused by spleen-kidney weakness with downward pouring of damp-heat. Symptoms include excessive vaginal discharge, yellow in colour like thick tea, with a fishy, foul odour, a red tongue, and a yellow greasy tongue coating. This type of vaginal discharge disorder is relatively common in clinical practice, and Yi Huang Tang, through its distinctive actions, can effectively improve the patient's symptoms and restore bodily health.

IV. Formula Analysis

1. Combining Tonifying the Spleen and Boosting the Kidneys with Clearing Heat and Dispelling Dampness

The formula uses a heavy dosage of Shanyao and Qianshi to tonify the spleen and boost the kidneys, addressing the root cause. When spleen qi functions vigorously and kidney essence is sufficient, the body's righteous qi is robust and able to resist external pathogens. Simultaneously, Huangbai and Cheqianzi are combined to clear heat and dispel dampness, treating the symptomatic manifestation of downward pouring of damp-heat. Treating both root and manifestation allows the spleen and kidneys to be tonified, the damp-heat to be cleared, and the vaginal discharge to naturally cease.

2. Combining Astriction with Clearing and Disinhibiting

Shanyao and Qianshi have the action of astringing and consolidating to stop vaginal discharge, capable of constraining the slippage pattern of the lower burner. Huangbai and Cheqianzi clear and disinhibit damp-heat, giving the damp-heat pathogen an exit route. Astriction and clearing-disinhibition work together: this both astringes and consolidates to stop vaginal discharge, preventing further progression of the condition, and clears the damp-heat pathogen, avoiding its lingering retention — achieving a good therapeutic effect.

3. Synergistic Herb Action

Shanyao and Qianshi work synergistically with Huangbai and Cheqianzi, jointly exerting their effects. The spleen-tonifying and kidney-boosting action of Shanyao and Qianshi creates a favourable internal environment for Huangbai and Cheqianzi to clear and disinhibit damp-heat, making the heat-clearing and dampness-disinhibiting potency more focused; while the heat-clearing and dampness-disinhibiting action of Huangbai and Cheqianzi, in turn, helps Shanyao and Qianshi better exert their spleen-tonifying and kidney-boosting efficacy, avoiding the generation of damp-heat from excessive tonification. The entire formula's combination is rigorously structured, with each component complementing and enhancing the other.

V. Comparison with Related Formulas

1. Comparison with Wandai Tang

Wandai Tang also originates from the Fu Qingzhu Nuke, with its primary actions being tonifying the spleen and soothing the liver, and transforming dampness to stop vaginal discharge. It is indicated for spleen deficiency with liver constraint, and turbid-damp vaginal discharge. Compared with Yi Huang Tang, Wandai Tang focuses on liver constraint with spleen deficiency, emphasising soothing the liver and strengthening the spleen as its primary action, with dispelling dampness and stopping vaginal discharge as secondary; Yi Huang Tang, by contrast, focuses on dual spleen-kidney depletion with downward pouring of damp-heat, with tonifying the spleen, boosting the kidneys, clearing heat, and dispelling dampness as its primary action. The two have differing emphases in pathomechanism, actions, and herb selection; accurate pattern differentiation according to the patient's specific symptoms is required for clinical application.

2. Comparison with Longdan Xiegan Tang

Longdan Xiegan Tang has the actions of draining excess fire from the liver and gallbladder, and clearing and disinhibiting damp-heat from the liver channel. It is indicated for liver-gallbladder excess-fire flaring upward and liver-channel damp-heat pouring downward. Unlike Yi Huang Tang, Longdan Xiegan Tang primarily targets liver-gallbladder excess fire or liver-channel damp-heat, with the disease location leaning toward the upper burner and the liver and gallbladder; Yi Huang Tang, by contrast, primarily targets spleen-kidney depletion with damp-heat pouring downward into the lower burner. The two differ markedly in aetiology, pathomechanism, disease location, and herb selection; careful differentiation is required for clinical application.

VI. Clinical Applications

1. Gynaecological Vaginal Discharge Disorders

Yi Huang Tang is widely applied in gynaecological clinical practice; for various types of vaginal discharge disorders, as long as the pattern corresponds to spleen-kidney weakness with downward pouring of damp-heat, it may be used. For abnormal vaginal discharge caused by fungal vaginitis, trichomonal vaginitis, and the like, manifesting as excessive vaginal discharge, yellow in colour, thick in consistency or like curdled bean dregs, with an unpleasant odour, accompanied by spleen-kidney weakness symptoms such as soreness and weakness of the lumbar region and knees and spirit fatigue with lassitude, Yi Huang Tang often achieves good therapeutic results.

2. Urinary System Infection

In urinary system infections, if symptoms such as frequent, urgent, painful urination appear, accompanied by excessive vaginal discharge, yellow colour, foul odour, a yellow greasy tongue coating, and a slippery, rapid pulse, with the pattern identified as spleen-kidney depletion with downward pouring of damp-heat, Yi Huang Tang may also be selected with modifications for treatment. Through tonifying the spleen, boosting the kidneys, and clearing and disinhibiting damp-heat, the symptoms of urinary system infection can be relieved and recovery promoted.

3. Intestinal Damp-Heat Diarrhoea

For diarrhoea caused by intestinal damp-heat, if accompanied by symptoms such as excessive, yellow-coloured vaginal discharge, with pattern differentiation showing manifestations of spleen-kidney weakness, Yi Huang Tang may also serve as a reference formula. The heat-clearing and dampness-dispelling herbs within the formula can clear intestinal damp-heat, while the spleen-tonifying and kidney-boosting herbs reinforce the body's righteous qi, helping in the treatment of diarrhoea.

VII. Clinical Modifications

1. For Red-Tinged Vaginal Discharge

Blood-cooling herbs such as Shengdi (Fresh Rehmannia Root), Chishao (Red Peony Root), and Mudanpi (Tree Peony Bark) may be added to cool the blood and stop bleeding, treating the symptom of red-tinged vaginal discharge. Shengdi can clear heat, cool blood, nourish yin, and generate fluids; Chishao clears heat, cools blood, disperses stasis, and relieves pain; Mudanpi clears heat, cools blood, activates blood, and resolves stasis — used together, the three reinforce the blood-cooling potency.

2. For Excessive Vaginal Discharge with Pronounced Spleen Deficiency

Spleen-strengthening and qi-boosting herbs such as Huangqi (Astragalus Root) and Dangshen (Codonopsis Root) may be added to reinforce the spleen-tonifying potency. Huangqi can tonify qi, raise yang, consolidate the exterior, stop perspiration, promote urination, reduce swelling, generate fluids, and nourish blood; Dangshen can strengthen the spleen, benefit the lungs, nourish blood, and generate fluids; the two, acting synergistically with Shanyao, better improve the spleen-deficiency symptoms.

3. For Pronounced Damp-Heat

Heat-clearing, dampness-drying, and toxicity-resolving herbs such as Tufuling (Smilax Rhizome) and Kushen (Sophora Root) may be added to reinforce the heat-clearing and dampness-dispelling effect. Tufuling can resolve toxicity, eliminate dampness, and unblock the joints; Kushen can clear heat, dry dampness, kill parasites, and relieve itching, producing excellent therapeutic effects for cases with more pronounced damp-heat.

VIII. Dosage and Preparation (Traditional Method and Modern Concentrated Granules)

1. Traditional Method

The traditional administration is by water decoction. Generally: Shanyao 1 liang (30 g), Qianshi 1 liang (30 g), Huangbai 2 qian (6 g), Cheqianzi 3 qian (9 g), and Baiguo (Ginkgo Seed) 10 pieces (crushed). Wash the herbs clean, place in the pot, add an appropriate amount of water, soak for approximately 30 minutes, then decoct over a low flame to 200–300 ml, taken in two administrations, one dose per day.

2. Modern Concentrated Granules

Modern concentrated granules are granule preparations produced from traditional Chinese herbs through extraction, concentration, and related processes, convenient to take. The dosage of modern concentrated granules of Yi Huang Tang generally corresponds to the concentrated equivalent of Shanyao 30 g, Qianshi 30 g, Huangbai 6 g, Cheqianzi 9 g, and Baiguo 10 pieces (crushed). Following the method specified in the product instructions, simply dissolve in boiled water; generally also taken in two administrations, one dose per day.

IX. Precautions and Contraindications

1. Dietary Restrictions

During the course of medication, spicy, greasy, and raw, cold irritating foods should be avoided. These foods readily add burden to the spleen and stomach, affecting herb absorption and therapeutic efficacy, and are unfavourable for recovery from the condition. Foods such as chilli peppers, fried foods, and ice cream should all be avoided as far as possible.

2. Constitutional Differences

Use with caution in those with a deficiency-cold constitution. Yi Huang Tang contains bitter-cold herbs such as Huangbai; those with a deficiency-cold constitution may, after taking the formula, experience damage to yang qi, aggravating cold patterns. For example, patients with spleen-stomach deficiency-cold who frequently experience abdominal pain and diarrhoea, prefer warm foods, and have cold hands and feet should use this formula cautiously under medical guidance.

3. Special Circumstances

Use with caution in pregnancy. Although Yi Huang Tang generally has no marked toxicity, the action of the herbs within the formula is relatively complex; to ensure fetal safety, pregnant women requiring its use must do so under strict medical supervision.

X. Modern Research

1. Pharmacological Action Research

Modern research has demonstrated that the herbs within Yi Huang Tang possess multiple pharmacological actions. Shanyao contains numerous nutritional constituents, such as amylase and polyphenol oxidase, capable of promoting digestion and absorption and strengthening the body's immunity. Qianshi has antioxidant and anti-inflammatory actions, providing a degree of protective benefit for the urinary and reproductive systems. Huangbai possesses antibacterial, anti-inflammatory, and antitumour activity, capable of inhibiting the growth of numerous bacteria and fungi. Cheqianzi has diuretic, anti-inflammatory, and expectorant actions, capable of improving urinary system function. These pharmacological actions provide a scientific basis for Yi Huang Tang's treatment of related conditions.

2. Clinical Efficacy Verification

Extensive clinical research has confirmed the effectiveness of Yi Huang Tang in treating vaginal discharge disorders and related conditions. Through observation of patients treated with Yi Huang Tang for vaginal discharge disorders, it has been found to significantly improve patients' vaginal discharge symptoms — such as volume, colour, consistency, and odour — while also markedly improving systemic symptoms such as soreness and weakness of the lumbar region and knees and spirit fatigue with lassitude. In treating conditions such as urinary system infections, Yi Huang Tang can also achieve good clinical efficacy, relieving patients' symptoms and improving their quality of life.

3. Dosage Form Improvement Research

With the development of modern science and technology, research into improving the dosage form of Yi Huang Tang has been ongoing. Beyond the traditional water decoction and modern concentrated granule forms, exploration is also underway to develop new dosage forms for Yi Huang Tang, such as capsules and tablets. These new dosage forms have the advantages of convenient administration and ease of storage, with the potential to provide patients with more options and further enhance the clinical application value of Yi Huang Tang.