Bo He

Bo He (Herba Menthae Haplocalycis) is the dried aerial parts of Mentha haplocalyx Briq., an aromatic perennial herbaceous plant in the family Lamiaceae (mint family). In the traditional TCM classification system, Bo He is considered pungent in flavor with a cool nature. It enters the Lung and Liver meridians, giving it a central role in formulas that address Wind-Heat exterior patterns, Liver Qi stagnation, and disorders of the head and throat.

Botanical description: Mentha haplocalyx is an erect or ascending perennial herb growing 30–60 cm tall. The stems are quadrangular, green or purplish, and frequently branched. The leaves are opposite, petiolate, ovate-lanceolate to oblong-lanceolate, 3–7 cm long and 1.5–3 cm wide, with a serrated margin and a characteristic crinkled surface. The leaf surface is glabrous or nearly so, with prominent veins on the lower surface. The plant produces small, purplish or white flowers in axillary whorls arranged in dense verticillasters, forming a terminal spike-like inflorescence. The entire plant is strongly aromatic, with a characteristic penetrating, cooling odor. The flowering top is harvested in summer and early autumn, then dried in the shade.

Habitat and cultivation: M. haplocalyx is widely distributed across China, including the provinces of Jiangsu, Zhejiang, Jiangxi, Hunan, and Sichuan. It is also found in Japan, Korea, and parts of Southeast Asia. The plant prefers sunny, moist environments and is commonly cultivated in fields, along riverbanks, and in waste areas. In China, commercial cultivation is extensive, with Jiangsu and Zhejiang provinces being the primary producing regions. The herb is typically harvested twice per year — the first cutting in June–July and the second in September–October. The aerial parts are cut above ground, tied into small bundles, and dried in a well-ventilated, shaded area to preserve the volatile oil content.

Quality markers: The Chinese Pharmacopoeia specifies that high-quality Bo He should have a strong, characteristic aromatic odor, a cool and pungent taste, and a high essential oil content (not less than 0.8% v/w on a dried basis). The leaves should be dark green with a crinkled surface, and the stems should be green to purplish-green. The pharmacopoeia also sets quality standards for the content of menthol and other marker compounds. Premium-grade material is characterized by its intense aromatic fragrance, dark green color, and absence of mold, insect damage, or excessive stem material.

In the traditional Chinese medicine theoretical framework, Bo He is understood in terms of its effects on specific patterns of disharmony (zheng). Because Bo He enters the Lung and Liver meridians and has a pungent, cool quality, it is traditionally indicated for a range of patterns involving Wind-Heat invasion and Liver Qi stagnation.

Dispersing Wind-Heat and relieving exterior patterns: Bo He is considered one of the most important herbs in TCM for dispersing Wind-Heat exterior patterns. In TCM theory, when Wind-Heat invades the exterior, the body may manifest as fever, slight chills, headache, sore throat, and a thin yellow tongue coating. Bo He is traditionally used to dispel the pathogenic factor through the skin, using its pungent, cool nature to release the exterior. It is a key herb in the classic formula Yin Qiao San (Honeysuckle and Forsythia Powder), one of the most widely used formulas for early-stage Wind-Heat invasion. In this context, Bo He is typically combined with Jin Yin Hua and Lian Qiao to enhance the Wind-Heat dispersing effect.

Clearing the head and eyes: Bo He is traditionally used for disorders of the head and eyes, particularly those involving Wind-Heat or Liver Fire. Symptoms such as red, swollen, painful eyes, dizziness, and headache are considered indications for Bo He. Its aromatic, dispersing nature is believed to carry its cooling effect upward to the head and eyes. It is commonly combined with Ju Hua and Sang Ye in formulas for Wind-Heat affecting the head and eyes. This traditional use is based on TCM pattern differentiation and should not be equated to specific ophthalmic diagnoses.

Soothing the throat: Bo He is a common herb for sore throat and throat discomfort, particularly when associated with Wind-Heat patterns. Its cooling and dispersing properties are believed to relieve throat congestion, reduce swelling, and alleviate pain. In TCM practice, Bo He is often used as a single herb in tea form or as a gargle for mild throat irritation. It is also a component of many classical formulas for throat disorders, where it is combined with herbs such as Jie Geng and Gan Cao.

Moving Liver Qi and relieving stagnation: Bo He enters the Liver meridian and is traditionally used to soothe the Liver and move stagnant Liver Qi. In TCM theory, Liver Qi stagnation may present as chest and rib-side distension, irritability, depression, sighing, and a feeling of a lump in the throat (plum pit sensation). Bo He is a minor but important ingredient in the classic formula Xiao Yao San (Free and Easy Wanderer), where it is added in small amounts to assist Chai Hu in soothing the Liver and relieving stagnation. Its aromatic, dispersing nature is believed to help smooth the flow of Liver Qi without being too harsh or drying.

Classical literature references: The Shen Nong Ben Cao Jing (Divine Farmer's Materia Medica Classic, circa 200 CE) classified Bo He as an upper-grade herb and recorded its traditional use for "evil qi, wind-cold headache, and stiffness of the joints." The Ben Cao Gang Mu (Compendium of Materia Medica, 1596 CE) by Li Shizhen noted Bo He's ability to "clear the head and eyes, benefit the throat, and move Liver Qi." The Ben Cao Bei Yao emphasized its dispersing nature and recommended caution in cases of Yin deficiency with excessive sweating.

Bo He contains a range of bioactive compounds that have been the subject of pharmacological investigation. The following overview summarizes the major chemical constituents identified in the aerial parts of Mentha haplocalyx and what is currently known about them from published research.

Menthol: Menthol is a cyclic monoterpene alcohol and the most abundant and well-characterized constituent of Bo He essential oil. It is responsible for the characteristic cooling sensation mediated through activation of the transient receptor potential melastatin 8 (TRPM8) channel. Menthol has been studied in pre-clinical and some clinical research for its analgesic, anti-inflammatory, antimicrobial, and local anesthetic properties. Topical menthol preparations are widely used in over-the-counter products for pain relief. However, most research on menthol has been conducted on the isolated compound rather than on whole-herb Bo He preparations, and the clinical relevance of these findings for oral TCM use is not well established.

Menthone: Menthone is a monoterpene ketone that is the second most abundant volatile constituent in Bo He essential oil. Studies have investigated menthone for its potential antimicrobial, antifungal, and insecticidal activities. Recent research has also explored its role in modulating histone acetylation and inhibiting fungal growth. Menthone contributes significantly to the characteristic aroma of Bo He. Its pharmacological contribution to the overall effects of whole-herb Bo He preparations is still being investigated.

Cineole (1,8-cineole / eucalyptol): Cineole is a monoterpene oxide present in Bo He essential oil. It has been studied for its anti-inflammatory, mucolytic, and bronchodilatory effects, particularly in the context of respiratory conditions. Some clinical studies have investigated cineole-containing preparations for their effects on cough, sinus congestion, and airway inflammation. The cineole content of Bo He varies depending on chemotype, growing conditions, and harvest time.

Rosmarinic acid: Rosmarinic acid is a phenolic ester found in Bo He and many other Lamiaceae plants. It has been studied in pre-clinical research for its antioxidant, anti-inflammatory, and antiviral properties. Rosmarinic acid is a known inhibitor of complement activation and has been investigated for its potential in treating allergic and inflammatory conditions. The levels of rosmarinic acid in Bo He are influenced by growing conditions, harvest time, and processing methods.

Linarin and hesperidin: These flavonoids have been isolated from the non-volatile fraction of Bo He. Linarin has been studied for its anti-inflammatory and neuroprotective effects in pre-clinical models. Hesperidin, a flavanone glycoside widely distributed in citrus and mint plants, has been investigated for its antioxidant, anti-inflammatory, and vascular protective properties. Both compounds represent minor constituents of the overall Bo He profile but may contribute to its pharmacological effects.

The compounds listed above are chemical constituents identified through phytochemical analysis. Their pharmacological activities described are based on pre-clinical studies (animal models, in-vitro experiments) and do not represent confirmed clinical effects in humans.

Bo He is a component in several important classical formulas in the TCM tradition. Below are three key formulas that feature Bo He as a component, along with their traditional indications and the role Bo He plays in each composition.

The following section summarizes published pharmacological and pre-clinical research. Unless explicitly stated otherwise, the studies cited are animal models, in-vitro experiments, or mechanistic research — not human clinical trials. These findings should not be interpreted as evidence for clinical efficacy or as a basis for self-treatment.

Antimicrobial activity of Bo He essential oil: The essential oil of Mentha haplocalyx has been studied for its antimicrobial properties against a range of bacterial and fungal pathogens. Research by Zhang et al. (2015) demonstrated that the essential oil exhibited contact toxicity and repellent activity against the cigarette beetle Lasioderma serricorne. More recent work by Zhang et al. (2026) showed that vacuum fractional distillation of Bo He essential oil significantly enhanced its antibacterial activity against Xanthomonas citrisubsp. citri by disrupting cell membrane integrity and inhibiting biofilm formation (PMID: 41350077). Liao et al. (2024) reported that a nanoemulsion formulation of Bo He essential oil exhibited inhibitory activity against Fusarium oxysporumgrowth (PMID: 38992117). These findings provide mechanistic insights into the antimicrobial potential of Bo He, but their clinical relevance for human infections has not been established.

Anti-inflammatory and antioxidant effects: Chen et al. (2017) investigated the phenolic fraction of M. haplocalyx and its constituent linarin in lipopolysaccharide-induced RAW264.7 macrophage cells. The study found that the phenolic fraction and linarin significantly reduced the production of pro-inflammatory mediators through inactivation of the NF-kappaB and MAPK signaling pathways (PMID: 28509854). Jiang et al. (2020) isolated a galactan polysaccharide (WMP) from M. haplocalyx with structural characteristics that showed antioxidant and antiaging activities in pre-clinical models (PMID: 32070549). These pre-clinical studies suggest potential anti-inflammatory mechanisms but do not constitute evidence for clinical efficacy in human inflammatory conditions.

Neuroprotective and analgesic effects: Zeng et al. (2022) purified menthol and menthone from M. haplocalyx and investigated the neuroprotective effect of menthol on amyloid-beta toxicity in vitro through molecular docking studies (PMID: 35597196). Wang et al. (2026) demonstrated that didymin, a flavonoid constituent found in M. haplocalyx, alleviated neuropathic pain in animal models by targeting RKIP-mediated NF-kappaB/NLRP3 crosstalk to inhibit pyroptosis and neuroinflammation (PMID: 41453551). These findings are mechanistically interesting but are derived from animal and in-vitro models and should not be extrapolated to clinical applications.

Polysaccharide bioactivity: Ji et al. (2025) isolated an acid polysaccharide (MHa) from M. haplocalyxand demonstrated that it exerted antifatigue effects in an animal model through activation of AMPK signaling (PMID: 39864693). This research adds to the growing body of evidence that non-volatile constituents of Bo He, including polysaccharides, may contribute to its pharmacological profile. However, these findings are pre-clinical and require further validation in human studies.

What the research does NOT show: Despite promising pre-clinical signals, the research on Bo He and its active compounds does NOT demonstrate conclusive clinical efficacy for any specific disease in humans. There is no robust evidence from large-scale, randomized, placebo-controlled clinical trials that Bo He can treat, cure, or prevent infectious diseases, inflammatory disorders, or any other medical condition. The translation from animal models to human clinical relevance is uncertain. This page does not endorse Bo He as a treatment for any condition.

Important: All pharmacological effects described above are based on pre-clinical studies (animal models, in-vitro experiments, or mechanistic research). They do not constitute evidence of clinical efficacy in humans. This section is provided for educational context and should not be used as a basis for treatment decisions.

General safety profile: Bo He is widely used in TCM practice and is generally considered to have a favorable safety profile when used appropriately at standard doses in formula combinations. However, like all herbal products, it is not free of risk. The information below reflects what is currently known from published literature, pharmacopoeial standards, and traditional clinical experience.

Yin deficiency and excessive sweating: In traditional TCM theory, Bo He is pungent and dispersing in nature. Individuals with Yin deficiency — characterized by dry mouth, night sweats, a red tongue with little coating, and a thin, rapid pulse — should use Bo He with caution, as its dispersing nature may further deplete Yin fluids. Similarly, individuals with spontaneous sweating or excessive sweating due to Qi deficiency should avoid high doses or prolonged use, as Bo He's dispersing action may exacerbate fluid loss. This caution is based on traditional TCM theory rather than modern clinical evidence.

Spleen-Stomach deficiency-cold: Bo He is cool in nature, and its prolonged use or use at high doses may theoretically weaken the digestive function in individuals with Spleen-Stomach deficiency-cold patterns. Symptoms such as poor appetite, abdominal distension, loose stools, and a pale tongue with white coating may be worsened by the cool nature of Bo He. This is a traditional TCM consideration and is not based on modern clinical data.

Pregnancy and lactation: Bo He is generally considered safe during pregnancy when used in moderate amounts as part of a TCM formula under professional guidance. However, high doses of menthol have been shown in some pre-clinical studies to have uterine stimulant effects, and the essential oil should be avoided during pregnancy, especially in concentrated forms. Self-administration of Bo He products during pregnancy is not recommended. Bo He should only be used during pregnancy under the direct supervision of a qualified healthcare professional.

Pulegone content and safety: Pulegone is a monoterpene ketone present in small amounts in some Menthaspecies, including M. haplocalyx. At high doses, pulegone has been shown to cause hepatotoxicity in animal models. Huan et al. (2025) investigated pulegone-induced liver injury in mice and found that CYP2E1 inhibition did not reduce its toxicity, suggesting complex mechanisms of hepatotoxicity (PMID: 40249652). The pulegone content of Bo He is generally low, and standard doses of Bo He in TCM practice are not associated with liver toxicity. However, concentrated essential oil products and prolonged high-dose use of Bo He should be avoided. Quality control measures in the Chinese Pharmacopoeia help ensure that pulegone levels remain within acceptable limits.

Drug interactions: Pre-clinical data suggest that menthol and other constituents of Bo He may affect hepatic cytochrome P450 enzyme activity, particularly CYP3A4 and CYP2C9, which could theoretically alter the metabolism of drugs processed through these pathways. The essential oil components may also have additive effects when combined with central nervous system depressants. Additionally, menthol may enhance the percutaneous absorption of topical medications. Clinical interaction data for whole-herb Bo He are very limited. Consult a qualified healthcare professional before combining Bo He with any prescription medications.

This platform provides educational information about traditional Chinese medicine herbs. It does not recommend, endorse, or prescribe the use of Bo He or any other herbal product for the treatment of any medical condition. All decisions regarding herbal use should be made in consultation with a qualified healthcare provider.