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EXTERIOR-RELEASING HERBS:
TCM & WESTERN PERSPECTIVES

By John Chen, L.Ac., O.M.D., Pharm.D., Ph.D.

Definition: Substances that ‘release the exterior’ act to dispel pathogenic factors from the external and superficial parts of the body.

The term ‘pathogenic factors’ describes normally benign environmental factors, such as wind, cold or heat, that have combined to disrupt normal physiological functioning and express themselves in the form of wind-cold and wind-heat. With drastic or sudden changes in the weather, or with a decline in health or immunity, these factors commonly attack the exterior or superficial parts of the body, that is, the skin and muscle layers. Therefore, an ‘exterior syndrome’ refers to a condition characterized by wind-cold or wind-heat attacking (or ‘invading’) the skin and muscle layers of the body, causing symptoms and signs such as aversion to cold, chills, fever, headache, muscle aches and pain, the inappropriate presence or absence of perspiration, and a superficial pulse.

The herbs in this category stimulate immune response, alleviate pain, regulate body temperature, and induce perspiration. They are most often used to treat common colds, influenza, and complications of complex internal disorders.

SUBCATEGORIES OF ACTION

Clinically, exterior-releasing herbs fall into two categories to address the problems of exterior wind-cold or exterior wind-heat syndromes.

Dispel wind-cold: These herbs are generally acrid and warm in thermal property. They induce perspiration, dispel wind-cold from the exterior, and promote warming and relaxation of the skin and muscle layers.

Dispel wind-heat: These herbs are commonly acrid and cold substances in thermal property. They dispel wind-heat to relieve fever and pain or inflammation in the throat, eyes and skin.

Herbs from both categories are generally used in the treatment of common colds, influenza, bacterial infections, asthma, coughing, wheezing, measles, chest congestion, nausea, vomiting, edema, arthritis, and eye disorders. Herbs that release the exterior may also serve multiple purposes: to regulate qi circulation to relieve pain, relieve wheezing and dyspnea, dissolve phlegm, promote the eruption of measles, relieve nausea and vomiting, regulate water circulation and eliminate dampness, and brighten the eyes.

DIFFERENTIAL DIAGNOSIS AND TREATMENT

Accurate differential diagnosis of the external pathogen and the degree to which it has penetrated is of vital importance: treatment of wind-cold and wind-heat can be significantly different. Furthermore, it is important to determine the basic underlying condition of the patient prior to prescribing any herbal formula.

Pre-existing constitutional deficiency or chronic illness may require the addition of tonics to enhance the overall therapeutic effect. However, tonics must not be used alone or casually in the presence of an exterior condition, as this will only send the pathogenic factors deeper into the interior of the body, thus complicating the illness.

Differential Diagnosis of Wind-Cold and Wind-Heat
Diagnosis	Symptoms	Tongue	Pulse
Wind-cold	aversion to cold, fever, absence of perspiration, headache, body aches and pain	thin and white tongue coat	superficial, tight pulse

Wind-heat	fever, mild aversion to wind and cold, dry or sore throat, thirst	thin and yellow tongue coat	superficial, rapid pulse

CAUTIONS/CONTRAINDICATIONS

Many herbs that release the exterior do so via inducing perspiration. Overdose, prolonged use, or inappropriate use of these herbs will consume qi and body fluids, resulting in qi deficiency, dryness and/or yin deficiency. Therefore, they should be used only when necessary. Furthermore, intake of these herbs should be discontinued immediately, when the desired therapeutic results are achieved.

Herbs that release the exterior should be prescribed with caution for individuals who have a deficiency of qi, yin, blood or body fluids. Exterior-releasing herbs should be used with caution in patients with an exterior condition accompanied by sores and abscess, lin zheng (dysuria syndrome), or bleeding.

PROCESSING

Many herbs that release the exterior are aromatic and contain volatile essential oils. Cooking these herbs for a prolonged period of time causes evaporation and destruction of many active constituents. Therefore, these more volatile herbs (often leaves and flowers) should be added at the end of the cooking time for the main formula, so that they are only decocted briefly, simmering for no more than 5 minutes, long enough to release their potent influence without diminishing their actions. The practice of adding the herb at the end of the cooking process is referred to in this text as “post-decoction.”

PHARMACOLOGICAL EFFECTS

Diaphoretic: Many herbs in this category induce perspiration. Of these herbs, Ma Huang (Herba Ephedrae) exerts the strongest diaphoretic function by directly stimulating the sweat glands, as verified by in vivo and in vitro studies. The effect of Ma Huang may be potentiated by the addition of Gui Zhi (Ramulus Cinnamomi), which dilates peripheral blood vessels and increases blood circulation to the superficial parts of the body. Among other herbs that have both diaphoretic and antipyretic influences are Sheng Jiang (Rhizoma Zingiberis Recens) and Bo He (Herba Menthae).

Antipyretic: Many exterior-releasing herbs reduce body temperature in subjects experiencing either elevated or normal body temperature (in the case of normal temperature, these substances may bring body temperature below normal levels). The mechanisms of antipyretic action vary depending on the herb. Ma Huang (Herba Ephedrae), Gui Zhi (Ramulus Cinnamomi) and Bo He (Herba Menthae) act on the central nervous system and disperse heat via diaphoresis. Gui Zhi (Ramulus Cinnamomi), Sheng Jiang (Rhizoma Zingiberis Recens) and Bo He (Herba Menthae) reduce body temperature by promoting blood circulation to superficial parts of the body, dilating blood vessels, and opening skin pores to release heat. In addition, these three herbs have anti-inflammatory, antibacterial and antiviral actions that contribute to reducing body temperature. Other herbs with antipyretic effects include Zi Su Ye (Folium Perillae), Jing Jie (Herba Schizonepetae), Fang Feng (Radix Saposhnikoviae), and Bai Zhi (Radix Angelicae Dahuricae).

Sedative: Some herbs that relieve the exterior also exert a sedative influence, such as Gui Zhi (Ramulus Cinnamomi), Sheng Jiang (Rhizoma Zingiberis Recens), Chai Hu (Radix Bupleuri), Jing Jie (Herba Schizonepetae), and Fang Feng (Radix Saposhnikoviae). Administering these herbs reduces spontaneous physical activities (such as restlessness, spasms and twitches), and potentiates the effect of barbiturates.

Antibiotic: Both antibacterial and antiviral properties are integral to certain exterior-releasing herbs, such as Ma Huang (Herba Ephedrae), Gui Zhi (Ramulus Cinnamomi), Zi Su Ye (Folium Perillae), Chai Hu (Radix Bupleuri), Fang Feng (Radix Saposhnikoviae), Bo He (Herba Menthae), Gao Ben (Rhizoma Ligustici), Xiang Ru (Herba Elsholtziae seu Moslae), Xin Yi Hua (Flos Magnoliae) and Man Jing Zi (Fructus Viticis). Others may have only antibacterial or antiviral effects.

Metabolic: Many exterior-releasing herbs act to lower blood glucose levels, as is the case with Sang Ye (Folium Mori) and Ge Gen (Radix Puerariae). Others, like Ma Huang (Herba Ephedrae), stimulate the basal metabolic rate.

Diuretic: Some herbs in this category promote diuresis to eliminate excess water accumulation, including: Ma Huang (Herba Ephedrae), Fu Ping (Herba Spirodelae), Niu Bang Zi (Fructus Arctii), Mu Zei (Herba Equiseti Hiemalis) and Xiang Ru (Herba Elsholtziae seu Moslae).

Cardiovascular: Herbs such as Ge Gen (Radix Puerariae) and Ju Hua (Flos Chrysanthemi) increase perfusion of blood to the coronary arteries.

Antispasmodic: Jing Jie (Herba Schizonepetae), Ma Huang (Herba Ephedrae), Ge Gen (Radix Puerariae), and others relax the smooth muscles to prevent spasms and cramps.

Analgesic: In vitro and in vivo studies confirm that many herbs simultaneously relieve pain and release pathogens at the exterior levels. Fang Feng (Radix Saposhnikoviae) relieves pain via its effect on the central nervous system. Sheng Jiang (Rhizoma Zingiberis Recens) reduces inflammation and pain via its effect on the peripheral nervous system. Other analgesic herbs include Jing Jie (Herba Schizonepetae), Qiang Huo (Rhizoma et Radix Notopterygii), Man Jing Zi (Fructus Viticis), Gao Ben (Rhizoma Ligustici), and Xin Yi Hua (Flos Magnoliae), but the mechanisms of their actions are not well understood at this time.

Anti-inflammatory: Chai Hu (Radix Bupleuri) reduces inflammation by stimulating the release of hormones from the adrenal cortex. Qiang Huo (Rhizoma et Radix Notopterygii) reduces inflammation by stimulating the endocrine system, particularly the pituitary gland and adrenal cortex. Sheng Jiang (Rhizoma Zingiberis Recens) and Ma Huang (Herba Ephedrae) exert their anti-inflammatory effect by inhibiting prostaglandin synthesis in the periphery.

Antivenin: Some exterior-relieving herbs are useful as antidotes for snake bites, such as Bai Zhi (Radix Angelicae Dahuricae).

POTENTIAL HERB-DRUG INTERACTIONS

Exterior-releasing herbs are characterized by diaphoretic action, inducing perspiration. Some achieve this by stimulating sweat glands, others by dilating peripheral blood vessels. Herbal diaphoretic activity is generally not associated with reported or potential herb-drug interactions.

Sedatives: Herbs that release the exterior have many other pharmacological effects, as described above, and therefore may interact with other medicinal agents. For example, the sedative influence may be potentiated when one takes both herbs and drugs with sedative properties. The sedative effect of the herbs may also be potentiated by intake of alcohol. Excessive sedation interferes with alertness, increasing the risk of injury if one drives an automobile or operates heavy machinery.

Antibiotics: Antibiotic activity may be potentiated by concurrent use of herbs and drugs.

Diuretics: Some exterior-releasing herbs promote diuresis. Therefore, it is prudent to avoid combining those herbs with drugs that exert diuretic effects, as there may be additive or synergistic results. Inappropriate combination therapy may lead to excessive loss of fluids and electrolytes.

ABOUT THE AUTHOR

John Chen, L.Ac., O.M.D., Pharm.D., Ph.D.

Dr. John Chen is a recognized authority in both western pharmacology and Chinese Herbal Medicine, having combined formal training in both fields with extensive research ‘on the ground’ in China. He teaches at the USC School of Pharmacy, Emperor’s College, Yo San University of TCM, OCOM, Five Branches, AOMA and ACTCM, and has taught numerous professional seminars across the U.S. and internationally. Dr. Chen’s published works include Chinese Medical Herbology and Pharmacology (2003, AOM Press) and the upcoming Chinese Herbal Formulas and Applications (2008, AOM Press) for which works he is lead author.

This article was taken out of Dr. Chen’s book Chinese Medical Herbology and Pharmacology.
To order a copy, click here.

To learn more about herbs, John Chen is speaking on the following topic for Lotus Institute. The class is approved for 8 CEUs/PDAs by the California Acupuncture Board and NCCAOM.

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