Yin Qiao San

Yin Qiao San (Lonicera and Forsythia Powder) is the representative acrid-cool exterior-releasing formula created by the famous Qing Dynasty physician Wu Ju-tong (Wu Tang), recorded in his masterpiece Wen Bing Tiao Bian (1798). The name "Yin" refers to Jin Yin Hua (Lonicera japonica), "Qiao" refers to Lian Qiao (Forsythia suspensa), and "San" refers to the powder dosage form, which is taken decocted with fresh Lu Gen soup or mixed with boiling water.

In the TCM formula classification system, Yin Qiao San belongs to the exterior-releasing formulas (jie biao ji) and specifically the acrid-cool exterior-releasing formulas (xin liang jie biao ji). Wu Ju-tong positioned it as an "acrid-cool balanced formula" — between the acrid-cool light formula Sang Ju Yin and the acrid-cool heavy formula Bai Hu Tang. This classification reflects Wu Ju-tong's layered medication thinking for treating defensive-level warm disease: mild cases use Sang Ju Yin to lightly diffuse Lung qi; moderate cases use Yin Qiao San to clear heat and resolve toxicity while penetrating the exterior; severe cases use Bai Hu Tang to vigorously clear qi-level heat-toxin.

The formula design of Yin Qiao San embodies the Warm Disease School treatment principle of "treating the defensive level by sweating" — that is, using acrid-cool penetrating and dispersing methods to allow warm-heat pathogen at the exterior level to be resolved through sweating, while also clearing heat and resolving toxicity to prevent the pathogen from penetrating deeper. Since its creation, this formula has been a foundational formula for clinical treatment of wind-heat common cold and early-stage warm disease in TCM, and is an essential formula for exterior-releasing formulas in TCM education.

Yin Qiao San originates from Wu Ju-tong's Wen Bing Tiao Bian (1798, Qing Dynasty, Jiaqing era). Wu Ju-tong (1758-1836), named Tang, styled Ju-tong, was from Huai'an, Jiangsu, and was one of the great synthesizers of the Qing Dynasty Warm Disease School, together with Ye Tian-shi, Xue Xue, and Wang Meng-ying known as the "Four Great Masters of Warm Disease." He devoted decades to studying warm disease theory, and on the basis of inheriting Ye Tian-shi's Wen Re Lun academic thought, combined with his own clinical practice to write this classic work of warm disease studies.

Wen Bing Tiao Bian · Upper Jiao Chapter records: "For Taiyin wind-warmth, warm-heat, warm-epidemic, and winter-warmth at the early stage with aversion to wind-cold, use Gui Zhi Tang; for heat without aversion to cold with thirst, use the acrid-cool balanced formula Yin Qiao San." Wu Ju-tong positioned Yin Qiao San as the main formula for treating early-stage Taiyin (Lung) warm disease with pathogen at the defensive level, applicable to the pattern characteristic of "heat without aversion to cold with thirst." In his formula discussion, he elaborated on the formulation principle: "The excellence of this formula lies in its pre-emptive protection of deficiency, purely clearing and draining the upper jiao without offending the middle and lower jiao, without the drawback of opening the door to bandits, yet with the ability to remove excess through lightness."

It is worth noting that in the process of creating Yin Qiao San, Wu Ju-tong absorbed previous medication experience. The idea of combining Jin Yin Hua, Lian Qiao, and Gan Cao has certain origins in formulas from the Song Dynasty Tai Ping Hui Min He Ji Ju Fang; while the combined use of Bo He and Niu Bang Zi reflects the deep understanding of acrid-cool exterior-releasing medicinals by warm disease physicians of the Ming and Qing dynasties. Wu Ju-tong's innovation lies in organically combining these medicinals to form the unique formula architecture of "acrid-cool exterior penetration with heat-clearing and toxicity-resolving."

Since its creation, Yin Qiao San has been widely used in clinical practice and highly praised by physicians of successive generations. Qing Dynasty physician Wang Shi-xiong (Meng-ying) cited the formulation thinking of Yin Qiao San in Wen Re Jing Wei; modern physician Zhang Xi-chun also discussed this formula in Yi Xue Zhong Zhong Can Xi Lu. After the founding of the People's Republic of China, Yin Qiao San was included in successive editions of the Pharmacopoeia of the People's Republic of China, becoming one of the commonly used standardized TCM formulas. Modern prepared Chinese medicines such as "Yin Qiao Jie Du Pian" and "Yin Qiao Jie Du Granules" are developed on the basis of Yin Qiao San.

The following composition reflects records from classical TCM literature. Specific dosages vary by historical version and individual condition and are not intended as medication advice.

Yin Qiao San is composed of ten medicinals, using the "Emperor-Minister-Assistant-Envoy" compatibility structure. In the formula, Jin Yin Hua and Lian Qiao are Emperor herbs, acrid-cool exterior-penetrating and heat-clearing toxicity-resolving; Bo He, Niu Bang Zi, Jie Geng, and Dan Dou Chi are Minister herbs, dispersing wind-heat and diffusing the Lung to benefit the throat; Zhu Ye and Gan Cao are Assistant herbs, clearing heat and generating fluids while harmonizing medicinals; Jing Jie Sui is Envoy herb, acrid-warm dispersing, assisting Emperor herbs in penetrating the exterior. The whole formula is mainly acrid-cool, assisted by a small amount of acrid-warm, together achieving the effect of "acrid-cool exterior penetration and heat-clearing toxicity-resolving."

Formula Explanation

The formulation logic of Yin Qiao San can be understood from the following Emperor-Minister-Assistant-Envoy structure:

• Jin Yin Hua (Emperor): Sweet and cold in nature, entering the Lung, Stomach, and Heart channels. Functions to clear heat and resolve toxicity, disperse wind-heat, and can also penetrate the nutritive qi and transform the qi level, being a key medicinal for treating warm disease at the defensive level. Modern research shows that chlorogenic acid and luteolin glycoside in Jin Yin Hua have antiviral, anti-inflammatory, and antibacterial pharmacological activities. As one of the Emperor herbs, Jin Yin Hua dominates the heat-clearing and toxicity-resolving direction of the formula.
• Lian Qiao (Emperor): Bitter and slightly cold in nature, entering the Lung, Heart, and Small Intestine channels. Functions to clear heat and resolve toxicity, reduce swelling and nodules, and disperse wind-heat. Lian Qiao has strong heat-clearing and toxicity-resolving power, and can also clear heart heat and eliminate vexation, complementing Jin Yin Hua perfectly. Modern research shows that forsythin and forsythiaside in Lian Qiao have antiviral, anti-inflammatory, and antioxidant effects. Jin Yin Hua and Lian Qiao together as Emperor herbs establish the treatment direction of "acrid-cool exterior penetration with heat-clearing and toxicity-resolving" for the formula.
• Bo He (Minister): Acrid and cool in nature, entering the Lung and Liver channels. Functions to disperse wind-heat, clear the head and eyes, benefit the throat, and promote eruption of papules. Bo He has strong acrid-cool dispersing power, helping wind-heat pathogen to be resolved from the exterior. Menthol and menthone in Bo He have fever-reducing, anti-inflammatory, and analgesic pharmacological effects.
• Niu Bang Zi (Minister): Bitter, acrid, and cold in nature, entering the Lung and Stomach channels. Functions to disperse wind-heat and resolve toxicity to benefit the throat. Niu Bang Zi is especially good at clearing the throat and is an essential medicinal for treating wind-heat sore throat. Arctiin in Niu Bang Zi has anti-inflammatory and antiviral pharmacological activities.
• Jie Geng (Minister): Bitter, acrid, and neutral in nature, entering the Lung channel. Functions to diffuse the Lung and transform phlegm, benefit the throat and stop cough, and carry medicinals upward. In the formula, Jie Geng not only directly treats cough and sore throat, but more importantly "carries medicinals upward" — guiding the power of all medicinals upward to the Lung system (throat and respiratory tract), playing the role of a "boat and oar medicinal."
• Zhu Ye (Assistant): Sweet, bland, and cold in nature, entering the Heart, Lung, and Stomach channels. Functions to clear heat and generate fluids, promote urination and eliminate vexation. In the formula, Zhu Ye guides heat-toxin out through the urine, providing an outlet for heat pathogen, embodying the treatment thinking of "giving the pathogen an outlet."
• Gan Cao (Assistant): Sweet and neutral in nature, entering the Heart, Lung, Spleen, and Stomach channels. Functions to clear heat and resolve toxicity and harmonize all medicinals. In the formula, Gan Cao both assists in clearing heat and resolving toxicity and moderates the medicinal nature, preventing the formula from being excessively cold.
• Jing Jie Sui (Envoy): Acrid and slightly warm in nature, entering the Lung and Liver channels. Functions to release the exterior and disperse wind, promote eruption of papules and stop itching. Adding a small amount of acrid-warm Jing Jie Sui to a formula dominated by acrid-cool medicinals embodies the "counter-assistant" compatibility thinking of "assisting acrid-cool with acrid-warm," enhancing the formula's exterior-penetrating and dispersing power so that wind-heat pathogen is resolved from the exterior.
• Dan Dou Chi (Minister/Envoy): Sweet, acrid, and cool in nature, entering the Lung and Stomach channels. Functions to release the exterior and eliminate vexation, disperse constrained heat. In the formula, Dan Dou Chi both assists Emperor and Minister herbs in dispersing exterior pathogens, and also has the effect of dispersing constrained heat and eliminating vexation to calm the spirit.

The formulation of Yin Qiao San embodies the core treatment thinking of the Warm Disease School of "acrid-cool exterior penetration with heat-clearing and toxicity-resolving," and also demonstrates the exquisiteness of the "Emperor-Minister-Assistant-Envoy" compatibility theory in TCM formula science. Through the combined use of acrid-cool and acrid-warm, the simultaneous attention to exterior penetration and interior clearing, and the coordination of Lung diffusion and throat benefit, this formula achieves comprehensive treatment of wind-heat exterior patterns.

The following are traditional TCM pattern descriptions, not modern medical diagnoses, and do not constitute treatment recommendations.

• Wind-Heat Exterior Pattern (Wind-Heat Common Cold) — The most classical application pattern of Yin Qiao San. Clinical manifestations include prominent fever, mild aversion to cold, absence of sweating or slight sweating, headache, red and swollen sore throat, cough, dry mouth with mild thirst, red tip of tongue, thin white or thin yellow coating, and floating rapid pulse. In TCM theory, this pattern is caused by wind-heat pathogen invading the Lung-wei (skin and hair and Lung), with wei qi constrained and Lung failing to diffuse and descend. Yin Qiao San disperses wind-heat through acrid-cool exterior penetration while also clearing heat and resolving toxicity, making it the representative formula for this pattern.
• Early-Stage Warm Disease (Defensive-Level Pattern) — The initial stage of warm disease (warm-heat disease), with pathogen at the defensive level, manifesting as fever, mild aversion to cold, headache, cough, sore throat, and thirst. Yin Qiao San was positioned by Wu Ju-tong as an "acrid-cool balanced formula," suitable for the early stage of warm disease when pathogen is in the Lung-wei. Its treatment thinking is "treating the defensive level by sweating" — through acrid-cool dispersing, allowing warm-heat pathogen at the exterior level to be resolved through sweating, preventing the pathogen from penetrating deeper into the qi level and nutritive-blood level.
• Wind-Heat Invading the Lung — A wind-heat pattern with cough as the main symptom, manifesting as frequent coughing, loud cough sound, thick yellow phlegm, sore throat, nasal congestion with yellow discharge, fever, and mild aversion to cold. Yin Qiao San improves Lung diffusion and descent functions by dispersing wind-heat and diffusing the Lung to stop cough.
• Heat-Toxin Sore Throat — A pattern with red, swollen, and painful throat as the main manifestation, often accompanied by fever, difficulty swallowing, and swollen tonsils. In Yin Qiao San, Jin Yin Hua and Lian Qiao clear heat and resolve toxicity, while Niu Bang Zi and Jie Geng benefit the throat and stop pain, having a good effect in relieving sore throat.

Modern research on Yin Qiao San covers whole-formula extracts, single herbs, and their active components at multiple levels. The following are the main contents of various research reports and do not represent verified clinical treatment recommendations. Research evidence quality varies and should be interpreted cautiously.

Level 1: Single Herb and Active Component Research

The active components of the main herbs in Yin Qiao San have been relatively extensively studied pharmacologically:

• Jin Yin Hua (Chlorogenic Acids). Chlorogenic acid and its isomers in Jin Yin Hua are among the main active components. Research shows that chlorogenic acid has broad-spectrum antibacterial, antiviral, anti-inflammatory, and antioxidant effects. A systematic review published in Phytomedicine (Chen et al., 2021) summarized the antiviral activity of Jin Yin Hua, reporting inhibitory effects on influenza virus, respiratory syncytial virus, adenovirus, and other viruses. In vitro studies show that Jin Yin Hua extract exerts anti-inflammatory effects through modulating the TLR4/NF-κB signaling pathway.
• Lian Qiao (Forsythin, Forsythiaside). Forsythin and forsythiaside in Lian Qiao are its main active components. Research shows that forsythiaside A has antiviral, anti-inflammatory, and neuroprotective effects. A review published in Journal of Ethnopharmacology (Wang et al., 2020) summarized the pharmacological activities of Lian Qiao, including anti-influenza virus, antibacterial, anti-inflammatory, and antioxidant effects. Lian Qiao extract showed inhibitory effects on influenza A virus (H1N1, H3N2) in vitro experiments.
• Niu Bang Zi (Arctiin). Arctiin and arctigenin in Niu Bang Zi have anti-inflammatory, antiviral, and immunomodulatory activities. Research shows that arctigenin can alleviate inflammatory responses by inhibiting the TLR4/MyD88/NF-κB signaling pathway and has shown inhibitory effects on influenza virus replication in vitro.
• Bo He (Menthol). Menthol in Bo He has fever-reducing, analgesic, anti-inflammatory, and local anesthetic effects. Bo He extract has also shown certain antiviral activity in vitro experiments.

Important note: Most of the above studies are based on single-herb extracts or purified active components, not complete Yin Qiao San whole-formula preparations. Interactions between components may occur during decoction of the whole formula, and its pharmacodynamic characteristics may differ from single-herb research results.

Level 2: Whole-Formula Research — Antiviral and Fever-Reducing

Research on the whole Yin Qiao San formula has mainly focused on antiviral, fever-reducing, and anti-inflammatory effects. A study published in Chinese Journal of Natural Medicines (Liu et al., 2019) reported that Yin Qiao San whole-formula extract has inhibitory effects on influenza A virus (H1N1) in vitro and can alleviate virus-induced inflammatory responses by modulating the RIG-I/NF-κB signaling pathway. Another study (Zhang et al., 2020) using Yin Qiao San whole-formula in an influenza virus-infected mouse model observed that the formula can reduce lung viral load, alleviate lung tissue inflammatory damage, and regulate Th1/Th2 immune balance.

Regarding fever-reducing effects, some animal experiments reported that Yin Qiao San whole-formula extract has fever-reducing effects in yeast-induced fever rats, and its mechanism may be related to reducing hypothalamic cAMP and PGE2 levels. In addition, some clinical observational studies (mainly in Chinese literature) reported the clinical efficacy of modified Yin Qiao San formulas for treating upper respiratory tract infections, but these studies commonly have limitations such as small sample sizes, inadequate randomization, and lack of strict controls.

Level 3: Whole-Formula Research — Anti-inflammatory and Immunomodulatory

The anti-inflammatory effects of Yin Qiao San whole formula have been preliminarily verified in multiple animal experiments. Research shows that Yin Qiao San extract can reduce levels of pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1β in bronchoalveolar lavage fluid in a lipopolysaccharide (LPS)-induced acute pneumonia mouse model. Its anti-inflammatory mechanism may be related to inhibiting activation of the NF-κB and MAPK signaling pathways. In addition, some studies have explored the immunomodulatory effects of Yin Qiao San, reporting that it can enhance macrophage phagocytic function and regulate T-lymphocyte subset ratios, but related evidence is still in preliminary stages.

Overall Evidence Limitations

The main limitations of modern research evidence on Yin Qiao San are as follows: most clinical studies were published in Chinese journals with small sample sizes (usually n=30-100) and uneven research design quality; large-scale, multi-center, randomized double-blind placebo-controlled trials are lacking; most clinical studies used modified formulas rather than the original formula, making it difficult to evaluate the exact efficacy of the original formula; whole-formula pharmacokinetic studies are still insufficient, and the absorption, distribution, metabolism, and elimination processes of active components in vivo have not been fully elucidated; long-term safety data is lacking; bioequivalence between different preparations (decoction, powder, granules) has not been systematically evaluated. Therefore, existing evidence is insufficient to support definitive efficacy of Yin Qiao San for any specific disease.