Ho wood

Ho Wood: A Comprehensive Reference

1. Identity and Botanical Classification

1.1 Names and Taxonomy

Ho wood refers to the essential oil and aromatic preparation derived from a specific chemotype of Cinnamomum camphora (L.) J. Presl — the linalool-dominant chemotype. Its full botanical designation is Cinnamomum camphora var. linaloolifera Y. Fujita. The INCI (International Nomenclature of Cosmetic Ingredients) name is "Cinnamomum Camphora Linalooliferum Wood Oil."

Synonyms include Cinnamomum camphora linalooliferum, Cinnamomum camphora var. linalool, and Cinnamomum camphora ct. linalool. In French it is called Bois de Hô or Bois de Shiu; other English names include Ho Leaf, Ho Wood, and Shiu Rosewood. It is also commonly known as Shiu Wood, Camphor Tree, Camphor Laurel, and Chinese Bay.

The naming landscape surrounding this species is a frequent source of confusion in commerce. The Latin name Cinnamomum camphora can refer both to the camphor tree from Madagascar, whose leaf distillation produces the essential oil of ravintsara rich in 1,8-cineole (Cinnamomum camphora CT cineole), as well as the Shiu (or Ho) tree, whose wood distillation produces an essential oil rich in linalool (Cinnamomum camphora CT linalool).

1.2 The Plant: Morphology and Natural Habitat

Cinnamomum camphora is native to China, Japan, and Taiwan, with botanically similar sub-species now growing in many other countries. Camphor trees are large, often reaching heights of 30 meters (100 feet) or more, with a broad, spreading crown with a straight trunk. Ho Leaf and Ho Wood trees are tall evergreens belonging to the Lauraceae family reaching heights of up to 20 meters, with glossy leaves and cream-colored flowers.

Originally labeled "stink camphor" in Taiwan due to its low camphor content, it was later renamed "aromatic camphor" because of its high linalool content, giving it a pleasant aromatic fragrance. Although closely resembling camphor, it is regarded as a variant or subvariant of camphor, with smaller flowers and fruits.

1.3 Chemotypes of Cinnamomum camphora

The botanical species Cinnamomum camphora has several chemotypes that are a result of its different conditions of growth, such as climate, soil, altitude, etc. There are six different chemical variants or chemotypes: camphor, linalool, 1,8-cineole, borneol, nerolidol, and safrole. The chemotypes are dependent on the geographical origin of the tree and the part of the tree used, e.g., leaf or wood/bark.

The three most commercially important distinct essential oils of Cinnamomum camphora are produced from three different chemotypes: Hon Sho — the camphor chemotype — which produces camphor oil; Ho Sho — the linalool chemotype — which produces Ho Wood oil; and Yu Sho — the cineole chemotype — which produces ravintsara oil. Ravintsara grows in Madagascar and primarily contains 1,8-cineole, the camphor tree is widespread in Vietnam and presents a camphor chemotype, while Ho Wood originates from China and predominantly contains linalool.

1.4 Extraction and Common Forms

Ho Wood essential oil is steam-distilled from the bark and wood (and sometimes the leaves are simultaneously distilled) of the same tree that brings us ravintsara essential oil. About 0.5% of the essential oil is extracted from the wood of Ho Wood through steam distillation, resulting in a colorless to pale yellow hue.

Ho Wood essential oil is described as a clear, mobile liquid of pale yellow color with a refreshing, sweet and slightly woody odor. Physical properties include a colorless to pale yellow appearance, a woody and floral scent, a density of 0.860–0.872 g/cm³, and a refractive index of 1.458–1.470.

The oil is commercially available in several forms: as a neat steam-distilled essential oil, as an organic-certified essential oil, and as a component in blended aromatherapy products, cosmetic formulations, and natural perfumes. A comparative investigation of essential oil compositions from different tissues of C. camphora has been carried out, with compositions evaluated through gas chromatography-mass spectrometry (GC-MS) and antimicrobial properties assessed by measuring minimum inhibitory concentrations (MICs).

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2. Traditional and Historical Use

2.1 East Asian Traditions

The fragrant camphor tree (Cinnamomum camphora) and its products have been coveted since ancient times, having a rich history of traditional use; it was particularly used as a fumigant during the era of the Black Death and considered as a valuable ingredient in both perfume and embalming fluid.

The Ho Wood presents a chemotype with linalool, which has been used for centuries in China and Japan. Historically, Ho Wood and its various components have been used in traditional Chinese medicine for various purposes. The tree's wood was commonly used to build temples and palaces, due to its aromatic quality and resistance to termites and other pests.

The camphor tree's Japanese name hints at its cultural and historical importance in Japan and its myriad practical uses. One theory proposes that クスノキ ("Kusunoki") originates from the word クスリノキ "Kusuri-no-ki," which literally means "tree of medicine." The medicine in question is camphor oil, which is derived from the wood and roots of the tree and has pain-relieving and anti-inflammatory properties.

Camphor obtained from camphor trees has long been used as a treatment for various symptoms such as inflammation, infection, congestion, muscle pain, and irritation in various regions. The camphor tree's leaves and bark have been used in traditional medicine across Asia for centuries, believed to have properties that can treat everything from colds to rheumatism.

2.2 Commercial and Industrial History

C. camphora is cultivated for camphor and timber production. The production and shipment of camphor, in a solid, waxy form, was a major industry in Taiwan prior to and during the Japanese colonial era (1895–1945). It was used medicinally and was also an important ingredient in the production of smokeless gunpowder and celluloid.

Historically, camphor trade was highly active. Marco Polo noted that camphor had been exported from Southeast Asia to the Middle East since the 6th century. By the 17th century, European botanists documented the camphor laurel on voyages to Taiwan and Japan; the Dutch East India Company began exporting "Japan camphor" to Europe where it was used in patent medicines and as a moth repellent.

Prior to the First World War, most camphor traded internationally originated from natural stands in Taiwan, with Chinese production being used locally. When natural stands became depleted, plantations were established, first in Taiwan and after the Second World War in Japan.

The rise of Ho Wood essential oil in cosmetic and fragrance applications can be traced back to 1985, when a major explosion at a linalool-producing facility created a demand for new sources of this compound. With high content of calming linalool and a similar scent profile to Brazilian Rosewood, Ho Wood has become a more sustainable alternative to the endangered Brazilian Rosewood in aromatherapy and perfumery formulations.

2.3 Traditional Medicinal Preparations

Ho Wood essential oil has a rich history rooted in traditional Asian practices, where it has been used for centuries in perfumery and incense. Derived from the wood of the Cinnamomum camphora tree, this oil has long been valued for its soothing and aromatic qualities, making it a cherished component in cultural rituals and wellness routines.

Camphor has long been used as an insect repellent, especially of moths in clothing, and was one of the first antiseptics used in hospitals. The various essential oils obtained from Cinnamomum camphora are important in perfumery mainly as sources of specific aroma chemicals, as fixing agents, and in scenting soaps. The wood is often considered too valuable to be used as timber, except for cabinet work such as chests for linen and clothes, with the fine odor of the wood and its observation that it repelled insects leading to the first extraction of the oil.

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3. Chemical Composition

3.1 Primary Constituent: Linalool

Ho Wood is one of the most potent sources of naturally occurring linalool found in any steam-distilled essential oil. Linalool (C₁₀H₁₈O), also called 3,7-dimethyl-1,6-octadien-3-ol, is a monoterpene alcohol broadly present as a major constituent of plant essential oils. In the linalool chemotype of C. camphora, linalool is the overwhelmingly dominant compound. Linalool has been reported at 98.7% of total composition in some analyses of the Ho leaf/wood fraction.

The dominance of the aromatic monoterpene alcohol linalool in Ho Wood oil bestows a warm, dainty, slightly rosy, sweet, woody fragrance to the oil.

3.2 GC-MS Profile of the Wood and Other Tissues

Different plant tissues of C. camphora have different extraction yields, with the leaf having the highest yield. GC-MS analysis revealed the presence of 18, 75, 87, 67, 67, and 74 compounds in leaf, branch, wood, root, leaf/branch, and leaf/branch/wood fractions, respectively.

Different parts (roots, wood, branch, and leaf) of Cinnamomum camphora L. are abundant in essential oils, which have linalool, 1,8-cineole, and camphor as major components. The wood essential oil showed the best antibacterial activity against Serratia marcescens among tested bacterial strains with an MIC of 39.1 μg/mL.

GC-MS studies examining non-linalool chemotype leaf material have identified camphor as the dominant component in some specimens. The main components of a camphor-type essential oil from C. camphora leaves were identified by GC-MS to be D-camphor (40.54%), linalool (22.92%), cineole (11.26%), and 3,7,11-trimethyl-3-hydroxy-6,10-dodecadien-1-yl acetate (4.50%). This illustrates how greatly the composition varies by chemotype: in the dedicated linalool chemotype (Ho Wood), linalool supplants camphor as the dominant fraction.

A GC×GC-TOFMS study identified a total of 96 components in the essential oils of C. camphora, with the main constituents found in the leaves and twigs being camphor, eucalyptol, linalool, and 3,7-dimethyl-1,3,7-octatriene. According to previous studies, C. camphora can be divided into five chemical types by the main compounds of its leaf oils: camphor-type, linalool-type, cineol-type, isonerolidol-type, and borneol-type.

3.3 Minor Constituents

Beyond its overwhelmingly linalool-dominant profile, the Ho Wood oil may contain trace quantities of other monoterpenes and sesquiterpenes. Camphor oil production centers around the Guangdong, Guangxi, Jiangxi, and Fujian provinces of China. Variability in minor constituents is influenced by geography, the specific part of the tree distilled, and whether bark, wood, or leaves contribute to the distillation. The 87 compounds identified by GC-MS in the wood fraction indicate a complex minor chemistry underlying the linalool-dominant profile.

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4. Pharmacology and Mechanisms of Action

Because Ho Wood essential oil is essentially a highly concentrated natural source of linalool, the known pharmacology of this monoterpene alcohol is directly relevant to the oil's biological activity. The following mechanisms have been identified in preclinical research.

4.1 Anti-Inflammatory Mechanisms

In models of LPS-induced inflammation, linalool inhibited the synthesis of TNF-α, IL-1β, nitric oxide (NO), and prostaglandins E2 (PGE2) through activation of the Nrf2/heme oxygenase-1 (HO-1) signaling pathway, and LPS-induced NF-κB activation was inhibited by linalool in a dose-dependent manner.

In vitro experiments demonstrated that linalool could inhibit the expression of IL-1β-induced inflammatory factors, including nitric oxide synthase, COX-2, nitric oxide (NO), prostaglandin E2 (PGE2), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α). Regarding mechanism, linalool was observed to inhibit signal transduction of NF-κB by activating the nuclear factor-erythroid 2-related factor-2 (Nrf2) in chondrocytes. This study demonstrates that linalool inhibits NF-κB by activating the Nrf2/HO-1 pathways, thereby suppressing the inflammatory response generated by IL-1β.

The monoterpene linalool exerts anti-inflammatory effects by inhibiting the signaling cascade starting with the transcription factor NF-κB. Effects include suppression of pro-inflammatory cytokines such as interleukin-1β and tumor necrosis factor-α, or through inhibiting the overexpression of COX-2 and prostaglandins, leading to suppression of leukotriene generation.

Studies in rats have found that linalool lowered thermal hyperalgesia provoked by carrageenan, PGE-2, and glutamate, as well as carrageenan-mediated paw edema and formalin-mediated nociception, implying a notable anti-inflammatory effect. Molecular docking has exhibited strong binding interaction of linalool with IL-17, iNOS, PGE-2, and COX-2.

4.2 Central Nervous System Mechanisms: Anxiolytic and Sedative

In mice, linalool odor has been shown to produce an anxiolytic effect without motor impairment in light/dark box and elevated plus maze tests. The effect was not observed in anosmic mice, indicating it was triggered by olfactory input evoked by linalool odor. The effect was antagonized by flumazenil, indicating that the linalool odor-induced anxiolytic effect was mediated by GABAergic transmission via benzodiazepine-responsive GABA_A receptors.

Using electrophysiological measurements, a non-selective suppression of voltage-gated sodium channels has been demonstrated in olfactory receptor neurons and Purkinje cells. Furthermore, linalool suppressed the function of excitatory glutamate receptors. In contrast to these suppressive effects, a potentiation of inhibitory GABA_A receptors has been previously reported. The observed potentiation at inhibitory GABA_A receptors is in agreement with the linalool effect on sedation and anxiety-related behaviors in mice.

Linalool has also been proposed to show anxiolytic and antidepressant effects by NMDA receptor blockade and inhibiting the reuptake of serotonin. In a mice model, inhaled linalool produced sedative effects, eliciting hypothermia, reducing locomotion, and increasing sleep time induced by pentobarbital.

4.3 Antimicrobial Mechanisms

Linalool exhibits antimicrobial activity against bacteria such as Escherichia coli, Listeria monocytogenes, Streptococcus pyogenes, Pseudomonas fragi, Staphylococcus aureus, Brochothrix thermosphacta, and Aeromonas hydrophila, as well as against fungi including Aspergillus flavus, Penicillium citrinum, Fusarium oxysporum, and Candida albicans.

Linalool, a monoterpene alcohol, showed concentration-dependent biofilm inhibition against Streptococcus pyogenes, with a maximum of 91% at a concentration of 0.004% (v/v). An AlamarBlue assay confirmed linalool's non-bactericidal anti-biofilm efficacy. Linalool treatment impeded micro-colony formation, mature biofilm architecture, surface coverage, and biofilm thickness, and impaired cell surface hydrophobicity and EPS production.

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5. Scientific Evidence by Area of Use

Important caveat: The clinical and scientific literature on Ho Wood essential oil specifically is very sparse. The bioactivity evidence discussed below pertains principally to linalool — Ho Wood's overwhelmingly dominant compound — studied either as an isolated chemical entity or within linalool-rich essential oils. Much of this evidence is preclinical (in vitro and animal models). Clinical human evidence directly attributable to Ho Wood essential oil specifically is essentially absent from the peer-reviewed literature as of the time of this writing.

5.1 Inflammation and Musculoskeletal Pain

Evidence level: Preclinical (in vitro and animal models) only.

A study assessed the anti-arthritic potential of linalool in a model of chronic joint inflammation (CFA-mediated rheumatoid arthritis) in rats. Linalool markedly lowered spleen and thymus indices compared to arthritic control. Over-formation of IL-17, COX-2, TNF-α, IL-1β, iNOS, and IL-6 was markedly impaired in all linalool-treated rats, but IL-10 was raised compared to arthritic animals in real-time PCR. There was also reduction in paw volume, arthritic index, mobility score, and flexion pain score.

In vitro experiments demonstrated that linalool could inhibit IL-1β-induced inflammatory factors including COX-2, NO, PGE2, IL-6, and TNF-α, and also reduced catabolism of the extracellular matrix by inhibiting expression of matrix metalloproteinase-13 (MMP-13) and ADAMTS5 while upregulating type II collagen (COL II) and aggrecan. Furthermore, linalool was observed to mitigate progression of osteoarthritis in a mouse model of DMM.

In analgesic assays using rodents, linalool at 200 mg/kg achieved a 93.80% writhing reduction in acetic acid-induced writhing tests, comparable to tramadol. A linalool-rich essential oil at 200 mg/kg inhibited carrageenan-induced edema by 51.35% at 4 hours, reduced IL-1β by 49.8%, and IL-6 by 26.5%, with effects comparable to ibuprofen. These are animal study findings only; equivalent human clinical evidence does not exist in the current literature.

5.2 Anxiety, Stress, and Neurological Applications

Evidence level: Predominantly preclinical (animal models and in vitro). Limited human-observation data exists for linalool as a component of lavender products, but not specifically for Ho Wood.

In mice experiments, linalool odor produced anxiolytic effects without motor impairment. The effect was absent in anosmic mice, confirming an olfactory mechanism, and was antagonized by flumazenil, indicating mediation via GABAergic transmission through benzodiazepine-responsive GABA_A receptors. These results provide a foundation for exploring clinical application of linalool odor in anxiety treatments.

The effectiveness of dietary supplements containing (3R)-(−)-linalool in the treatment of anxiety disorders has been confirmed by clinical trials. However, these trials specifically studied linalool-containing supplement formulations, not Ho Wood essential oil per se. Overall, evidence is mostly limited to preclinical studies and well-designed clinical trials are lacking. Nevertheless, existing data suggests that linalool is a relevant candidate for further investigation as a novel medicine for illnesses including anxiety, insomnia, and depression.

The potential antidepressant activity of NMDA receptor blocker compounds highlights a possible new target for linalool's antidepressant effect. The properties of linalool as an antagonist of NMDA receptors have been proposed through antinociceptive, analgesic, sedative, and anticonvulsant challenges. Linalool showed anxiolytic and antidepressant effects by NMDA receptor blockade and inhibiting the reuptake of serotonin.

Several studies on lavender oils (also high in linalool) have demonstrated the ability of these aromas to improve sleep in elderly people and infants. This indirect human evidence is suggestive but cannot be generalized to Ho Wood without specific clinical trials.

5.3 Antimicrobial Activity

Evidence level: Primarily in vitro. No clinical trials specific to Ho Wood exist.

Many studies have shown that linalool exhibits a variety of pharmacological activities, including analgesic, anxiolytic, sedative, anti-inflammatory, anti-tumor, and anti-bacterial effects.

A GC-MS and MIC study of C. camphora essential oils from different tissues showed that the wood essential oil demonstrated the best antibacterial activity against Serratia marcescens among tested bacterial strains, with an MIC of 39.1 μg/mL.

The current trend of employing compounds present in essential oils to support antibiotic therapy is becoming increasingly popular. Naturally occurring monoterpene constituents of essential oils are undergoing detailed studies to understand their effects on the human body, both independently and in doses correlated with currently used pharmaceuticals. However, all such evidence for linalool's antimicrobial activity remains in vitro or in vivo animal data; there are no published clinical trials evaluating Ho Wood essential oil as an antimicrobial in humans.

5.4 Skin Health and Dermatological Applications

Evidence level: Preliminary in vitro and observational. No dedicated clinical trials for Ho Wood.

Linalool per se is considered non-toxic and, according to recent in vitro and in vivo scientific studies, has demonstrated a comprehensive range of bioactive properties exploitable for pharmaceutical and cosmetic applications.

Ho Wood essential oil is known for its anti-inflammatory properties, which soothe irritated skin and itchy scalps. Its INCI-listed properties include anti-inflammatory and bactericidal characteristics. Linalool is considered an excellent fragrance additive for cosmetics, enhancing the preservative effect of formulations or acting as an anti-inflammatory agent on mild skin lesions.

Properties attributed to the Ho Wood essential oil in cosmetic contexts include soothing, fragrant, regenerating, revitalizing, anti-inflammatory, purifying, antibacterial, and toning effects, with suggested application to all skin types — particularly irritated, blemished, and mature skin — and all hair types, especially those with irritated scalps prone to itching.

5.5 Insect Repellent Activity

Evidence level: In vitro and laboratory bioassay data only.

In contact toxicity assays, essential oils from the leaves, twigs, and seeds of C. camphora exhibited strong insecticidal activity against cotton aphids, with LC₅₀ values of 245.79, 274.99, and 146.78 mg/L (after 48 hours of treatment), respectively. D-camphor and linalool both showed strong fumigant toxicity (LC₅₀ = 2.36 and 18.04 mg/L air, respectively) and contact toxicity (LD₅₀ = 13.44 and 12.74 μg/adult, respectively) against stored-product insect species.

5.6 Antioxidant Activity

Evidence level: In vitro only.

In addition to its anti-inflammatory and antioxidant properties, linalool also exhibits anti-cancer, sedative, anxiolytic, and anticonvulsant effects in preclinical research. A linalool-rich essential oil demonstrated potent antioxidant activity with an IC₅₀ of 32.04 μg/mL by DPPH radical scavenging assay, exceeding that of isolated linalool alone (IC₅₀ = 152.29 μg/mL). This suggests that the full essential oil matrix may provide synergistic antioxidant benefit beyond isolated linalool, but these findings are in vitro only.

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6. Body Systems and Health Areas

• Nervous system / psyche: Linalool has been extensively studied for its anxiolytic, sedative, and antidepressant potential, with preclinical evidence pointing to GABAergic, glutamatergic (NMDA), and serotonergic mechanisms. Linalool influences multiple neurotransmitter, inflammatory, and neurotrophic signals as well as behavior, demonstrating psychoactivity (albeit non-intoxicating).
• Musculoskeletal / inflammatory system: Reverse transcription-PCR analysis has demonstrated notable downregulation of pro-inflammatory markers including IL-1β, IRAK, NF-κB, TNF-α, and IL-17, alongside upregulation of the anti-inflammatory cytokine IL-10 in linalool-treated rats compared to controls.
• Integumentary system (skin and scalp): Anti-inflammatory and antibacterial properties of linalool support its use in topical formulations for irritated, blemished, and mature skin, and for inflamed scalp conditions.
• Immune/antimicrobial: Broad-spectrum preclinical antimicrobial activity against bacteria and fungi, with anti-biofilm properties demonstrated in vitro.
• Perfumery and cosmetic: The various essential oils obtained from Cinnamomum camphora are important in perfumery mainly as sources of specific aroma chemicals, as fixing agents, and in scenting soaps.

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7. Sustainability and Conservation Context

As Brazilian Rosewood essential oil faces sustainability concerns and regulatory restrictions, Ho Wood has come to serve as an ethical and eco-conscious substitute. As rosewood faces a decline, the Ho Wood tree has gained attention as a viable substitute.

C. camphora itself is facing pressure and threat, with increased interest in its value leading to indiscriminate use and a sharp drop in numbers, which could lead to extinction if appropriate protective measures are not taken. To preserve and protect this species, it is crucial to secure genetic diversity data.

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8. Dosage Forms and Reported Doses

No dedicated clinical dosage guidelines exist for Ho Wood essential oil as a distinct therapeutic agent. Dosage information in the literature pertains primarily to the study of isolated linalool in animal or in vitro models:

• Significant anticonvulsant effects in rodent models occurred at 200 mg/kg for both a linalool-rich essential oil and isolated linalool, increasing seizure latency by up to 87.20% and reducing seizure frequency by approximately 43%.
• In analgesic assays, linalool at 200 mg/kg achieved a 93.80% writhing reduction, comparable to tramadol.
• A hepatoprotection study administered linalool at 200 mg/kg/day orally in Wistar rats for two weeks.
• A dermal 90-day subchronic toxicity study conducted in rats determined a NOAEL (No Observed Adverse Effect Level) to be 250 mg/kg/day, based on reduced body weights.
• During inhalation studies, maximum transfer of linalool to the brain occurs after 90 minutes.

In cosmetic and topical aromatherapy practice, before any application to the skin, Ho Wood essential oil should be diluted — a 20% dilution in a vegetable oil has been cited as an upper reference limit for topical formulations. All mammalian dose data cited above pertain to animal research; no equivalent human therapeutic doses have been established in peer-reviewed clinical literature for Ho Wood oil itself.

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9. Safety Considerations

9.1 General Toxicology

Linalool per se is considered non-toxic, and according to recent in vitro and in vivo scientific studies, it has demonstrated a comprehensive range of bioactive properties that can be exploited for pharmaceutical and cosmetic applications. Safety evaluation studies have shown that linalool is not irritating, phototoxic, or allergenic per se, but has low-grade acute toxicity.

The U.S. Food and Drug Administration (FDA) includes linalool on its list of substances considered Generally Recognized as Safe (GRAS) as a flavoring substance. The safety of linalool has been evaluated by the Research Institute for Fragrance Materials Expert Panel (REXPAN), and based on this evaluation, an International Fragrance Association (IFRA) Standard has been established.

9.2 Skin Sensitization (Oxidation Products)

Based on the weight of evidence, linalool, in the absence of oxidation, does not present a concern for skin sensitization. However, autoxidation products of linalool are known to be contact allergens.

Linalool, and natural products rich in linalool, are subject to an IFRA standard that defines a good manufacturing practice (GMP) specification limiting peroxide levels to 20 mmol/L, with a recommendation to add an antioxidant at the time of production.

In a Confirmation of No Induction in Humans (CNIH) test, no reactions indicative of sensitization were observed with linalool at the maximum tested concentration of 12.7% (14,998 μg/cm²). Similarly, no reactions were observed in the human maximization test with 20% linalool in petrolatum.

The IFRA Standard restricts the use of linalool in fragrances because of potential sensitization from oxidized product. EU Cosmetic Regulation requires that the presence of linalool must be indicated in the list of ingredients when its concentration exceeds 0.001% in leave-on skin products and 0.01% in products that are rinsed off the skin.

9.3 NOAEL and Subchronic Toxicity

Repeated dose toxicity for linalool was determined using a read-across analog to have a most conservative systemic exposure-derived NOAEL of 36 mg/kg/day. A dermal 90-day subchronic toxicity study conducted in rats resulted in a margin of exposure (MOE) of 2,250 when considering 14.4% absorption from skin contact and 100% absorption from inhalation. A MOE of >100 is deemed acceptable.

9.4 Populations Requiring Caution

The essential oil of Ho Wood should not be used in pregnant women less than 3 months along, as well as in children under 3 years old. Given its high content of linalool, the essential oil of Ho Wood presents a high allergenic potential, particularly when oxidized. A patch test at the elbow bend before first application to the skin is recommended.

9.5 IFRA Standards

The International Fragrance Association (IFRA) has established category-specific usage limits for linalool to manage the risk from its autoxidation products. These limits vary by product type (e.g., leave-on versus rinse-off products, fine fragrance, body lotion, etc.) and are incorporated into good manufacturing practice standards for the fragrance industry. Fresh, stabilized (antioxidant-protected) formulations of Ho Wood essential oil present a significantly lower sensitization risk than oxidized or improperly stored material.

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10. Use in Perfumery and Cosmetics

In perfumery, Ho Wood is a valuable element in floral, floriental, and fougère-type fragrances. It blends seamlessly with essential oils such as ylang ylang, cedarwood, coriander, geranium, frankincense, rose, mandarin, orange, tangerine, lavender, and sandalwood.

Applications in cosmetic formulations include facial care (masks, serums, creams, cleansing gels), body care (body lotions/balms, hand and foot creams/lotions), and makeups (including lipsticks). Its soothing properties and high linalool content make it a valuable addition to skincare and personal care products, providing a gentle, aromatic experience.

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11. Summary of Evidence Strength

• Anti-inflammatory activity: Multiple, consistent preclinical studies (in vitro and animal models) for linalool; no human clinical trials specific to Ho Wood.
• Anxiolytic/sedative activity: Strong preclinical animal evidence for inhaled linalool with plausible GABAergic, serotonergic, and glutamatergic mechanisms; some human observational data for linalool-rich lavender preparations; no clinical trials for Ho Wood specifically.
• Antimicrobial: Robust in vitro evidence across numerous bacterial and fungal species; no clinical trials for Ho Wood as an antimicrobial agent.
• Skin health: Preclinical in vitro evidence and cosmetic formulation data; no dedicated clinical trials.
• Antioxidant: In vitro evidence only.
• Overall: Despite many studies focused on the essential oil of the camphor tree, there is a lack of systematic studies of its extraction or separation. Various components are not fully understood, and further research is needed on the medicinal effects of individual components of C. camphora.

References

• The Chemical Profiling of Essential Oils from Different Tissues of Cinnamomum camphora L. and Their Antimicrobial Activities — PMC/NCBI
• Advances in Research of Pharmacological Effects and Formulation Studies of Linalool — PubMed
• Linalool as a Therapeutic and Medicinal Tool in Depression Treatment: A Review — PMC/NCBI
• Natural Compounds in the Battle against Microorganisms—Linalool — PMC/NCBI
• Linalool Bioactive Properties and Potential Applicability in Drug Delivery Systems — PubMed
• Linalool Odor-Induced Anxiolytic Effects in Mice — PMC/NCBI
• Metabolic Products of Linalool and Modulation of GABA_A Receptors — PMC/NCBI
• A Review of the Potential Use of Pinene and Linalool as Terpene-Based Medicines for Brain Health — PMC/NCBI
• Phytochemistry and Applications of Cinnamomum camphora Essential Oils — PMC/NCBI
• Camphor—A Fumigant during the Black Death and a Coveted Fragrant Wood in Ancient Egypt and Babylon — PMC/NCBI
• GC×GC-TOFMS Analysis of Essential Oils Composition from Cinnamomum camphora — PMC/NCBI
• The Chemical Composition of Essential Oils from Cinnamomum camphora and Their Insecticidal Activity against Stored Product Pests — PMC/NCBI
• The Anti-Biofilm Potential of Linalool against Streptococcus pyogenes — PMC/NCBI
• Linalool: Monoterpene Alcohol Effectiveness in Chronic Synovitis — ScienceDirect
• Linalool Inhibits the Progression of Osteoarthritis via the Nrf2/HO-1 Signal Pathway — PubMed
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• Linalool — CosmeticsInfo.org (FDA GRAS / IFRA Standard)
• Chemical Composition and Antioxidant Activity of the Essential Oils of Citral-Rich Chemotype Cinnamomum camphora — PMC/NCBI
• Chemical Constituents and Insecticidal Activities of the Essential Oil of Cinnamomum camphora Leaves — Journal of Chemistry / Wiley
• Comprehensive Review on Linalool Biomedical Relevance — Drug Research / Thieme
• Pharmacological and Molecular Insights into Linalool-Rich Coriandrum sativum Essential Oil — PMC/NCBI
• Camphor Tree (Ho Leaf and Ho Wood) — THREE Holistic Research Center
• Ho Wood Essential Oil: Origin, Benefits, Uses — Typology
• Cinnamomum camphora — PROSEA / Plant Resources of South East Asia