Herbsmith Rx Er Chen San is a classical Chinese herbal formula recommended by holistic veterinarians to dry dampness, transform phlegm, regulate the qi, and harmonize the middle burner in dogs, cats, and horses. Also known as Two Cured Powder, Two Cured Soup, Lucid Channel, and Citrus and Pinella Formula, this four-herb formula from the Tai Ping Hui Min He Ji Ju Fang (Formulary of the Bureau of Peoples Welfare Pharmacies, Song dynasty, 1107 CE) is the foundational phlegm-transforming formula of the classical Chinese herbal tradition and the base from which hundreds of phlegm-treating formulas are derived. The formula's name Er Chen (Two Cured) refers to the two principal herbs Ban Xia (pinellia rhizome) and Ju Hong (red tangerine peel), both of which are aged and cured before use; the curing process for Ban Xia (processed with ginger to reduce its raw toxicity) and the aging of the citrus peel (older aged peel is more aromatic and effective) give the formula its name and reflect the traditional preparation standards that ensure the formula's safety and therapeutic effectiveness. The formula addresses three principal TCVM phlegm-damp patterns: Phlegm Damp Obstructing the Lungs (cough, mucus, respiratory congestion), Phlegm Rheum Abdominal Distension (digestive phlegm-damp accumulation, nausea, vomiting from phlegm obstruction of the middle jiao), and Phlegm Panting (labored breathing and panting from phlegm obstructing the lung qi's descending function). Well suited for dogs, cats, and horses presenting with the phlegm-damp pattern, characterized by productive cough with mucus or phlegm sounds from phlegm obstructing the lung qi, labored breathing or panting from phlegm obstruction, nausea and vomiting from phlegm accumulation in the middle jiao, reduced appetite and digestive disturbance from phlegm-damp obstructing the spleen and stomach, a pale or slightly dusky tongue with a white greasy or slippery coating reflecting the phlegm-damp accumulation, and a slippery pulse reflecting the phlegm and dampness. Available as a concentrated powder mixed into food; cats and dogs use the Canine Blend, while horses use the Equine/Horse Blend. Dosing varies by species and body weight, and your authorizing veterinarian will provide specific guidance.
VETERINARY AUTHORIZATION REQUIRED: Submit Your Authorization Request or Request a TCVM Telemedicine Consultation
What It Supports
- Phlegm transformation and dampness drying through Ban Xia as the principal phlegm-dissolving and dampness-drying herb addressing the phlegm-damp accumulation at its core: Transforms phlegm and dries dampness through Ban Xia (processed pinellia rhizome), the principal herb of the formula and the most potent phlegm-transforming herb in the classical materia medica. Ban Xia's acrid, warm, and drying nature directly dissolves and disperses accumulated phlegm in the lung, middle jiao, and channels, addressing phlegm formed from dampness accumulation due to the spleen's failure to transform and transport fluid. Ban Xia also descends rebellious stomach qi (addressing nausea and vomiting from phlegm obstruction of the middle jiao), dries dampness in the spleen and stomach (addressing the damp-phlegm substrate at the production source), and has a specific action of scattering phlegm nodules and lumps that form when phlegm accumulates in the channels and tissues over time. The processed (zhi) form used in Er Chen San is ginger-processed Ban Xia, which reduces the raw herb's toxicity (raw Ban Xia contains irritant calcium oxalate crystals and is not used clinically without processing) and adds ginger's warming, stomach-harmonizing action to Ban Xia's phlegm-transforming effect.
- Qi regulation and phlegm movement through Ju Hong's acrid aromatic action moving the lung and spleen qi to prevent phlegm re-accumulation from qi stagnation: Regulates the qi and assists in phlegm transformation through Ju Hong (red tangerine peel), the second of the two cured herbs and the qi-regulating complement to Ban Xia's direct phlegm-transforming action. Ju Hong (the red outer layer of tangerine peel, more aromatic and warming than Chen Pi, the fully dried tangerine peel) moves lung qi and spleen qi, dries dampness, and strengthens the spleen's transforming function. In Er Chen San, Ju Hong's qi-regulating role addresses the critical TCVM principle that phlegm accumulates when qi stagnates: when the spleen qi fails to transform and the lung qi fails to descend and disperse, fluid accumulates and congeals into phlegm. Ju Hong's acrid aromatic action moves the qi, preventing phlegm re-accumulation from qi stagnation, and its spleen-strengthening and dampness-drying action assists Ban Xia's dampness-drying from the spleen qi side. The aging of Ju Hong (older peel is more potent and less acrid) gives the formula its Two Cured name, alongside Ban Xia's ginger processing.
- Spleen strengthening and dampness drainage through Fu Ling, addressing the spleen qi vacuity root cause of the dampness accumulation that generates the phlegm: Strengthens the spleen and drains dampness through Fu Ling (poria, tuckahoe), the supporting herb that addresses the spleen qi vacuity root from which the phlegm-damp accumulation arises. In TCVM, the spleen transforms and transports fluids; when spleen qi is insufficient, fluid accumulates and congeals into phlegm and dampness. Fu Ling's spleen-strengthening and water-draining action addresses this root cause by reinforcing the spleen's transforming and transporting function and promoting the water metabolism that disperses the accumulated dampness before it can congeal further into phlegm. Fu Ling also has a gentle spirit-calming action through its heart-nourishing properties, which is relevant when phlegm obstruction generates the restlessness and agitation associated with phlegm misting the heart orifices. Fu Ling's water-draining action complements Ban Xia's dampness-drying and Ju Hong's qi-moving: together the three herbs address phlegm through transformation (Ban Xia), qi movement (Ju Hong), and spleen support with water drainage (Fu Ling).
- Harmonizing and moderating through Zhi Gan Cao coordinating the formula's herbs and protecting the spleen and stomach from the drying and dispersing intensity of Ban Xia and Ju Hong: Harmonizes and moderates the formula through Zhi Gan Cao (honey-fried licorice root), the harmonizing herb that coordinates the formula's phlegm-transforming and qi-moving herbs, moderates the potentially harsh drying action of Ban Xia and the aromatic dispersing action of Ju Hong, and provides mild spleen qi tonification that supports the formula's overall goal of restoring the spleen's dampness-transforming function. Zhi Gan Cao's honey-fried preparation enhances its spleen qi-tonifying and middle jiao-moistening action, which is important in a formula whose other three herbs are all drying or moving in nature; the Zhi Gan Cao prevents the formula from being so drying that it depletes the fluids needed for normal physiological function while still allowing the drying herbs to clear the pathological phlegm-damp. Zhi Gan Cao's harmonizing action also moderates the potential gastrointestinal irritation from Ban Xia and ensures the formula's four herbs work as a coordinated therapeutic whole.
TCVM Principles
- Primary action - foundational phlegm-damp transformation through the Er Chen San four-herb strategy addressing phlegm at the level of transformation (Ban Xia), qi movement (Ju Hong), spleen support (Fu Ling), and harmonization (Zhi Gan Cao): Addresses the phlegm-damp pattern through the most foundational and widely applicable phlegm-transforming strategy in the classical tradition, organized around four complementary actions that together address every aspect of phlegm-damp formation and persistence. The formula reflects the classical TCVM understanding that phlegm is not a substance that simply accumulates passively but is generated actively by the spleen's failure to transform and transport fluid (spleen qi vacuity or spleen yang insufficiency allows fluid to accumulate and congeal), maintained by lung qi's failure to descend and disperse (lung qi stagnation prevents the dispersal of fluid from the upper body), and perpetuated by qi stagnation in the middle jiao (qi stagnation thickens fluid into phlegm). Er Chen San addresses all three mechanisms: Ban Xia dissolves and transforms the already-formed phlegm; Ju Hong moves the qi to prevent phlegm re-formation from stagnation; Fu Ling strengthens the spleen to restore fluid transformation at the source; and Zhi Gan Cao harmonizes the whole strategy and protects the middle jiao from the drying herbs' potential for depleting normal fluids alongside the pathological phlegm.
- Secondary action - Er Chen San as the foundational base of the classical phlegm-treatment formula tradition, from which formulas for specific phlegm patterns are derived by adding targeted herbs to the core four-herb phlegm-transforming foundation: Er Chen San's position as the base formula of the Chinese phlegm-treatment tradition is as significant clinically as Er Miao San's position as the base of the damp-heat treatment series. Virtually every specialized phlegm formula in the classical canon builds on the Er Chen San core: Wen Dan Tang (Warm the Gallbladder Decoction) adds Zhu Ru and Zhi Shi to address phlegm-heat disturbing the heart spirit; Qing Qi Hua Tan Wan adds heat-clearing and phlegm-dissolving herbs for phlegm-heat in the lung; Di Tan Tang adds stronger phlegm-dissolving herbs for phlegm misting the heart orifices and generating wind; Dao Tan Tang (Guide Out Phlegm Decoction) adds Zhi Shi and Nan Xing for phlegm obstruction in the channels and generating wind; and Xiao Xian Xiong Tang's Half-Xia formulation echoes the Er Chen combination. The practitioner who understands Er Chen San's architecture understands the phlegm-treatment strategy that underlies the entire derived formula tradition.
Available Forms
- Powder - Canine Blend (for dogs and cats): Available in 75 g, 150 g, 500 g, 900 g, and 1200 g sizes; mix into food at the recommended dose for your pet's weight. Cats and dogs both use this blend.
- Powder - Equine/Horse Blend (for horses only): Available in 150 g, 500 g, 900 g, and 1200 g sizes; mix into grain at the recommended dose for your horse.
Suggested Use
For Dogs (Canine Blend Powder):
- Under 30 lbs: ½ tsp twice daily, or as prescribed
- 30-80 lbs: 1 tsp twice daily, or as prescribed
- 80-120 lbs: 1½ tsp twice daily, or as prescribed
- Over 120 lbs: 2 tsp twice daily, or as prescribed
For Cats (Canine Blend Powder): ¼ tsp twice daily, or as prescribed
For Horses (Equine/Horse Blend, 1,000 lb horse): Two tablespoons twice daily for 20 days, then two tablespoons once daily in grain. If the horse initially refuses, start with a small amount mixed into grain and gradually increase until the horse is accustomed to the taste. Most horses will readily accept the herbs in their grain.
Ingredients
Active Ingredients: Ban Xia (Rhizoma Pinelliae Ternatae), Ju Hong (Pericarpium Citri Erythrocarpae), Fu Ling (Sclerotium Poriae Cocos), Zhi Gan Cao (Honey-fried Radix Glycyrrhizae Uralensis)
Inactive Ingredient: Flaxseed
VETERINARY AUTHORIZATION REQUIRED: Submit Your Authorization Request or Request a TCVM Telemedicine Consultation
Active Ingredient TCVM Actions
Er Chen San is a four-herb formula organized around complementary actions: Ban Xia transforms phlegm and dries dampness as the principal herb; Ju Hong moves the qi and assists phlegm transformation as the associate herb; Fu Ling strengthens the spleen and drains dampness as the supporting herb; and Zhi Gan Cao harmonizes and moderates as the envoy herb:
- Ban Xia (Rhizoma Pinelliae Ternatae) - Pinellia Rhizome / Half Summer: Dries dampness, transforms phlegm, descends rebellious stomach qi, dissipates nodules, and reduces swelling; the principal phlegm-transforming herb of the formula and one of the most important herbs in the classical materia medica for the treatment of phlegm-damp patterns in any location. Ban Xia's acrid, warm, drying nature directly dissolves phlegm and dries the dampness from which phlegm is formed, descends the rebellious stomach qi that phlegm obstruction generates (addressing nausea, vomiting, and abdominal distension from phlegm obstruction of the middle jiao), and scatters phlegm nodules in the channels and tissues. Raw Ban Xia is toxic, containing irritant calcium oxalate crystals that cause severe mucosal irritation; the clinically used form is always processed, either ginger-processed (Sheng Jiang Ban Xia, as referenced in the classical Er Chen Tang decoction with fresh ginger) or alum-processed (Qing Ban Xia), which eliminates the raw toxicity and adds therapeutic benefit. Ban Xia may interact with anticholinergic medications because of its alkaloid content, and its strongly drying nature requires monitoring in animals with yin vacuity or dry conditions; the formula is contraindicated when phlegm stems from yin vacuity rather than damp-cold accumulation.
- Ju Hong (Pericarpium Citri Erythrocarpae) - Red Tangerine Peel / Erythrocarpa Citrus Peel: Regulates the qi, dries dampness, transforms phlegm, strengthens the spleen, and harmonizes the middle jiao; the second of the two cured herbs and the qi-regulating associate that prevents phlegm re-accumulation from qi stagnation. Ju Hong is the red outer layer of the tangerine peel, more aromatic, warming, and acrid than Chen Pi (fully dried tangerine peel), and with a stronger qi-moving and phlegm-drying action in the lung and upper body. In the Herbsmith Rx formulation, the ingredient listed as Pericarpium Citri Erythrocarpae reflects the classical Er Chen Tang use of aged red tangerine peel (ju hong) rather than standard Chen Pi. Ju Hong's aging is the second curing process referenced in the formula's name: older aged peel develops stronger aromatic compounds (limonene and related terpenes) that enhance its qi-moving and phlegm-dispersing action. Ju Hong has mild drug interactions through its flavonoid content (naringenin and related compounds) with CYP3A4-metabolized medications at high doses; standard therapeutic doses are unlikely to produce clinically significant interactions, but veterinary medication review is appropriate.
- Fu Ling (Sclerotium Poriae Cocos) - Poria / Hoelen / Tuckahoe: Strengthens the spleen and stomach, promotes water metabolism, drains dampness, calms the spirit, and tonifies the heart; the spleen-supporting and dampness-draining herb that addresses the root cause of the phlegm-damp accumulation by restoring the spleen's fluid-transforming function and promoting the water metabolism that disperses accumulated dampness before it congeals into phlegm. Fu Ling's spleen-strengthening action prevents phlegm re-accumulation by addressing the spleen qi vacuity that allows fluid to accumulate in the first place, and its water-draining action removes dampness through water-metabolism pathways (urinary dispersion) rather than only through drying. Fu Ling's gentle spirit-calming action is relevant when phlegm accumulation generates restlessness or agitation from phlegm obstructing the heart orifices. Fu Ling is generally well tolerated with minimal drug interactions; its water-promoting action warrants monitoring in animals on diuretic medications.
- Zhi Gan Cao (Honey-fried Radix Glycyrrhizae Uralensis) - Honey-fried Licorice Root: Tonifies the spleen qi, moistens and harmonizes the middle jiao, moderates the formula's herbs, and prevents the drying action of Ban Xia and Ju Hong from depleting normal physiological fluids alongside the pathological phlegm-damp; the harmonizing envoy herb that ensures the formula's drying strategy clears phlegm without generating dryness as a side effect. Zhi Gan Cao's honey-fried preparation enhances its spleen qi-tonifying and moistening action compared to raw Gan Cao, providing meaningful spleen support and middle jiao moistening in a formula where the other three herbs are all drying, moving, or draining in nature. At sustained doses, Gan Cao may interact with corticosteroids (pseudoaldosteronism-like effects), diuretics, and antihypertensive medications, and warrants veterinary review in animals on these medications.
Potential Drug Interactions
Er Chen San's principal drug interaction concern is Ban Xia's alkaloid content with potential anticholinergic interaction effects that warrant review in animals on anticholinergic or cholinergic medications; Ban Xia's strongly drying nature also creates a clinical contraindication in animals with yin vacuity dryness, and the formula should not be used when phlegm arises from yin vacuity heat generating thick, dry, difficult-to-expectorate phlegm rather than from damp-cold accumulation generating copious, thin, easy-to-expectorate phlegm. Ju Hong's flavonoid content (naringenin and related citrus flavonoids) has mild CYP3A4 interaction potential at high doses with cyclosporine, tacrolimus, statins, and other CYP3A4-metabolized medications; standard therapeutic doses are unlikely to produce clinically significant levels of inhibition, but veterinary medication review is appropriate in animals on narrow-therapeutic-index CYP3A4-metabolized drugs. Zhi Gan Cao at sustained doses has pseudoaldosteronism-like effects that can potentiate corticosteroids, antagonize diuretics, and interact with antihypertensive medications. The formula is appropriate only for phlegm-damp patterns with cold or neutral thermal character (white greasy tongue coating, slippery pulse, copious thin phlegm); it is not appropriate for phlegm-heat patterns (yellow tongue coating, thick yellow phlegm - requires heat-clearing herbs added to the base), yin vacuity phlegm (dry tongue, scanty coating, thick sticky phlegm - the drying herbs would worsen yin depletion), or presentations where the phlegm is from wind-phlegm generating tremors or seizures (requires different formula strategy).
Medication categories warranting extra caution include anticholinergic and cholinergic medications (Ban Xia alkaloid content), corticosteroids, diuretics, and antihypertensive medications (Zhi Gan Cao's sustained-dose pseudoaldosteronism-like effects), cyclosporine, tacrolimus, and other narrow-therapeutic-index CYP3A4-metabolized medications (Ju Hong flavonoid content at high doses), and diuretic medications (Fu Ling's water-promoting action). Your authorizing veterinarian will determine appropriateness based on your animal's condition, current medications, and confirmation of the phlegm-damp pattern through tongue quality (white greasy or slippery coating), pulse character (slippery pulse), and clinical assessment of the phlegm pattern's thermal character and tissue location.
VETERINARY AUTHORIZATION REQUIRED: Submit Your Authorization Request or Request a TCVM Telemedicine Consultation
Frequently Asked Questions
What conditions is Er Chen San used for in TCVM?
In Traditional Chinese Veterinary Medicine, Er Chen San is indicated for the phlegm-damp pattern in the lung, middle jiao, and channels, where dampness accumulates and congeals into phlegm that obstructs the qi movement and normal physiological function of the affected organ systems. Three principal presentations are addressed: Phlegm Damp Obstructing the Lungs, where phlegm accumulation in the lung channel obstructs the lung qi's descending and dispersing function and generates productive cough with mucus or phlegm sounds, congested breathing, and reduced respiratory capacity; Phlegm Rheum Abdominal Distension, where phlegm-damp accumulates in the middle jiao and obstructs the spleen and stomach function, generating nausea, vomiting, reduced appetite, abdominal distension, and loose stools from the spleen's failure to transform and transport; and Phlegm Panting, where phlegm obstruction in the lung channel prevents the lung qi from descending normally and generates labored breathing, panting, and respiratory distress from phlegm-damp obstruction. The tongue in the phlegm-damp pattern is pale or slightly dusky with a white, greasy, or slippery coating (the white, greasy coating is the most reliable clinical indicator of phlegm-damp), and the pulse is slippery (reflecting phlegm and dampness). Your authorizing veterinarian will differentiate the phlegm-damp pattern from phlegm-heat (which requires heat-clearing herbs added to the base), from yin vacuity phlegm (which requires yin-nourishing herbs rather than drying herbs), and from wind-phlegm generating neurological signs (which requires a different formula strategy).
How is Er Chen San administered to dogs, cats, and horses?
Mix the powder directly into food or grain at the dose recommended for your animal's species and body weight. Dogs and cats use the Canine Blend; horses use the Equine/Horse Blend. Dogs and cats receive the formula twice daily; horses receive two tablespoons twice daily for the first 20 days, then once daily for maintenance. Because Er Chen San contains Ban Xia with alkaloid content and drug interaction potential, and Zhi Gan Cao with sustained-dose interaction potential with corticosteroids, diuretics, and antihypertensives, your authorizing veterinarian must review all current medications before beginning use. Er Chen San is a phlegm-transforming formula that addresses both the accumulated phlegm (Ban Xia's transformation) and the spleen qi vacuity root (Fu Ling's spleen support); it is used for the duration of the phlegm-damp presentation and may be transitioned to a purely spleen-strengthening formula once the phlegm has been cleared, and only the underlying spleen qi vacuity remains to be addressed.
How long does it take to see results with Er Chen San?
As a phlegm-transforming and dampness-drying formula addressing an active phlegm-damp accumulation, Er Chen San typically produces results within a moderate timeframe that depends on the depth and duration of the phlegm-damp accumulation. Improvement in acute phlegm-obstructing presentations (productive cough, nausea from phlegm obstruction, phlegm panting) is often seen within 1 to 3 weeks as the formula's phlegm-transforming and qi-moving action begins clearing the phlegm accumulation. More complete resolution of chronic or deeply established phlegm-damp patterns, including normalization of the tongue coating from white and greasy to cleaner and thinner and return of the pulse from slippery to normal quality, typically requires 4 to 8 weeks or longer. Chronic phlegm-damp patterns where the spleen qi vacuity has been present for months or years, generating recurrent phlegm accumulation, may require sustained treatment and transition to a spleen-strengthening and phlegm-transforming maintenance formula after the acute phlegm accumulation has been cleared. Your authorizing veterinarian will monitor the tongue coating, pulse, and clinical phlegm signs throughout the treatment course.
What is the relationship between Er Chen San and other phlegm-treating formulas, and why is Er Chen San considered foundational?
Er Chen San is considered the foundational phlegm-treating formula of the classical Chinese herbal tradition because virtually every specialized phlegm formula in the classical canon is built by adding targeted herbs to the Er Chen San four-herb core, just as San Miao San and Si Miao San build on Er Miao San for damp-heat. The Er Chen San core of Ban Xia, Ju Hong, Fu Ling, and Zhi Gan Cao provides the essential phlegm-transforming, qi-moving, spleen-supporting, and harmonizing actions that address phlegm-damp at every level of its formation and persistence; specialized phlegm formulas then add herbs that direct this base action to specific tissue locations, thermal characters, or complicating pathogenic factors. Wen Dan Tang (Warm the Gallbladder Decoction) adds Zhu Ru (bamboo shavings, cools phlegm-heat) and Zhi Shi (immature bitter orange, moves qi more strongly) to the Er Chen base to address phlegm-heat disturbing the gallbladder and heart spirit, generating the anxiety, insomnia, and restlessness of phlegm-heat disturbing the shen. Qing Qi Hua Tan Wan adds Gua Lou, Huang Qin, and Dan Nan Xing to address phlegm-heat obstructing the lung with yellow phlegm and productive cough. Di Tan Tang adds Tian Nan Xing and stronger phlegm-dissolving herbs for phlegm misting the heart orifices and generating wind. Understanding Er Chen San's four-herb architecture and each herb's role helps practitioners see why specific herbs are added to each derived formula and what additional pathogenic factors they target beyond the core phlegm-damp pattern that Er Chen San alone addresses.