Thuja

Thuja (Thuja occidentalis L.): A Comprehensive Reference

1. Identity, Taxonomy, and Botanical Description

Thuja occidentalis L. (family Cupressaceae) has its origins in Eastern North America and is cultivated in Europe and Brazil as an ornamental tree, being known as the "tree of life" or "white cedar." It is a member of the Cupressaceae family and is known for its aromatic foliage and scale-like leaves. Unlike the closely related western red cedar (Thuja plicata), northern white cedar is only a small or medium-sized tree, growing to a height of 15 m (49 ft) tall with a 0.9 m (3.0 ft) trunk diameter.

The genus Thuja encompasses several species of medicinal importance, with T. occidentalis being the most studied. A distinct Asian species, Thuja orientalis (also known as Platycladus orientalis), is used in Ayurvedic and Chinese traditional medicine. The two species are not the same: both share terpenes but differ in thujone and minor constituents, yielding varied safety and efficacy profiles.

In the pharmacopeial literature, the dried young leafy twigs are the recognized herbal drug substance, referred to as Thujae occidentalis herba. For therapy, the dried herbal substance is used, which is called Thujae occidentalis herba. The total content of essential oils in dried young twigs was reported as 1.4 to 4%.

Common Names

• Arborvitae (Latin: "tree of life")
• Eastern White Cedar / Northern White Cedar
• White Cedar (North America)
• Lebensbaum (German)

Common Dosage Forms and Preparations

Extracts from the leaves and twigs have been prepared in various forms, including essential oils, tinctures, and homeopathic dilutions. Today, Thuja is primarily utilized in homeopathy, either as a mother tincture or in diluted forms. Additionally, it is combined with other immunomodulating plants, such as Echinacea purpurea, Echinacea pallida, and Baptisia tinctoria, as part of evidence-based phytotherapy for treating acute and chronic infections of the upper respiratory tract. The homeopathic remedy is prepared from a tincture of fresh leaves and young twigs, which are then potentised through the homeopathic process of serial dilution and succussion. Thuja extracts are frequently applied directly to the skin to address certain dermal growths, a practice rooted in traditional herbalism.

2. Traditional and Historical Use

Indigenous North American Traditions

Honoured with the name Nookomis Giizhik (Grandmother Cedar) in Ojibwe culture, the tree is the subject of sacred legends and is considered a gift to humanity for its myriad uses, among them crafts, construction, and medicine. It is one of the four plants of the Ojibwe medicine wheel, associated with the north. Thuja preparations with thujone were regularly used by American Indian traditional healers. The decoct and the tea prepared from the inner bark of the unwoody twigs could relieve constipation and headache. It has also been used for the treatment of polyps, birthmarks, and wounds, and as a painkilling and anthelmintic remedy.

The foliage is rich in vitamin C and is believed to be the annedda, which cured the scurvy of Jacques Cartier and his party in the winter of 1535–1536. This historical account is among the earliest recorded European encounters with the medicinal use of the plant.

Traditional European and Folk Medicine

Since historical times, the essential oil of T. occidentalis has been used in folk medicine. T. occidentalis containing thujone was used for hepatoprotection, bronchial catarrh, rheumatism, psoriasis, and even uterine carcinomas. In folk medicine, Thuja occidentalis has been used to treat bronchial catarrh, enuresis, cystitis, psoriasis, uterine carcinomas, amenorrhea, and rheumatism.

Traditional Use in Homeopathy

Arbor vitae (Thuja occidentalis L.) is a native tree widely used in homeopathy and evidence-based phytotherapy. The mother tincture of T. occidentalis is used in homeopathy against a number of diseases. Homeopathy uses Thuja as one of the main remedies for psychotic constitutions, in case of snake bite, small-pox, and vaccination-induced toxicity, as well as for the proliferation or pathological vegetation.

Summary of Traditional Indications Across Cultures

• In traditional medicine, it is commonly used to treat liver diseases, bullous bronchitis, psoriasis, enuresis, amenorrhea, cystitis, uterine carcinomas, diarrhea, and rheumatism.
• In traditional medicine, Thuja occidentalis has been employed for chronic bronchial inflammation, urinary incontinence, low urinary tract infection, chronic skin inflammation, uterine cancer, amenorrhea, and rheumatism.
• Treatment of warts, condylomas, and papillomas (across multiple traditions)

3. Phytochemistry: Key Constituents and Active Compounds

The chemical constituents of T. occidentalis have been of research interest for decades, due to their contents of essential oil, coumarins, flavonoids, tannins, and proanthocyanidines. The fresh plant contains approximately 0.6% essential oil (EO), 2.07% reducing sugars, 4.9% polysaccharides, 2.11% minerals, 1.67% free acids, and 1.31% tannic agents.

3.1 Essential Oil Fraction

The main monoterpenes identified in the EO obtained from fresh leaves are 65% thujone, 8% isothujone, 8% fenchone, 5% sabinene, and 2% α-pinene. Other identified monoterpenes include carvotanacetone, origanol, origanes, myrcene, and camphene. The dry plant has 1.4–4% EO, whose constituents include borneol, camphene, fenchone, limonene, myrcene, α-terpinene, terpinolene, thujone, and thujylalcohol. Thujone consists of 85% α-thujone and 15% β-thujone, and is the main compound (0.76–2.4%) found in the EO obtained from the dry plant.

GC and GC-MS analysis of four Thuja varieties cultivated in Poland identified 27–31 compounds in each variety. The main constituents in all samples were the monoterpene ketones α- and β-thujone, fenchone, and sabinene, as well as the diterpenes beyerene and rimuene. The total ketone content varied from 54.30–69.18% across samples.

3.2 Thujone: Chemistry and Identity

Thujone is the monoterpene found in the composition of many plants including Thuja occidentalis. However, the use of this compound is regulated by the European Parliament and Council and the European Medicines Agency. The isomers α-thujone and β-thujone are monoterpene ketones, with the IUPAC name: (1S,4R,5R)-4-methyl-1-(propane-2-yl) bicyclo(3.1.0)hexan-3-one. Thujone, which consists of 85% α-thujone and 15% β-thujone, is the major constituent in the essential oil from the dried herbal substance Thujae occidentalis herba.

The solvent for extraction significantly influences the amount of thujone in the extracts of the dried herbal substance Thujae occidentalis herba. The content of thujone in dried twigs was determined as 7.6 mg/g (0.76%), consisting of 85% α-thujone and 15% of the more toxic β-thujone.

3.3 Non-Volatile Constituents

Other compounds present in the dry plant are coumarins, represented by p-coumaric acid and umbelliferone; flavonoids including kaempferol, kaempferol-3-O-α-rhamnoside, mearnsitrin, myricetin, myricitrin, quercetin, and quercitrin; and tannins, (+/−)-catechins, (−)-gallocatechin, and proanthocyanidines, including procyanidin B-3 and prodelphinidin.

High molecular weight glycoproteins or polysaccharides have been shown to be particularly relevant for plant activity. The set of active contributors in Thuja occidentalis extracts mainly includes essential oils, flavonoids, and polysaccharides.

Recently, preclinical studies have identified the presence of polysaccharides, flavonoids, tannins, and proteins in the ethanol fraction, which showed antioxidant, hepatoprotective, antitumor, hypolipidemic, antidiabetic, and antiulcerative activities.

3.4 Bioactive Diterpenoids and Lignans

An ethyl acetate-soluble extract of the combined leaves and twigs of Thuja occidentalis was found to inhibit TPA-induced ornithine decarboxylase (ODC) in cultured mouse epidermal ME 308 cells. Bioassay-guided fractionation led to the isolation of six active constituents, namely (+)-7-oxo-13-epi-pimara-14,15-dien-18-oic acid, (+)-7-oxo-13-epi-pimara-8,15-dien-18-oic acid, (+)-isopimaric acid, (1S,2S,3R)-(+)-isopicrodeoxypodophyllotoxin, (−)-deoxypodophyllotoxin, and (−)-deoxypodorhizone. These compounds were evaluated for inhibition of the transformation of murine epidermal JB6 cells, inhibition of ornithine decarboxylase induction, and cytotoxic activity against KB cells.

4. Mechanisms of Action

4.1 Immunomodulatory Mechanisms

Thuja's antiviral action and immunopharmacological potential, such as stimulatory and co-stimulatory effects on cytokine and antibody production and activation of macrophages and other immunocompetent cells, have been evaluated in numerous in vitro and in vivo investigations.

Thuja polysaccharide g fraction (TPSg) was shown to be an inducer of the CD4+ fraction of the human peripheral blood T-cell subset. Furthermore, it could be demonstrated that TPSg is a potent inhibitor of the expression of HIV-1-specific antigens. TPSg induces IL-1β, IL-2, IL-3, IL-6, gamma-IFN, G-CSF, GM-CSF, and TNF-β production in peripheral blood lymphocyte cultures, and IL-1β and IL-6 in monocyte/macrophage cultures.

Other constituents include lignans and flavonoids like quercetin, and T-lymphocyte activation with an increase of cytokine distribution has been described. Furthermore, thujapolysaccharides appear to have antiviral properties.

4.2 Anti-inflammatory Mechanisms

A study highlighted the anti-inflammatory activity of the aqueous extract and the polysaccharide fraction obtained from T. occidentalis in experimental models of acute inflammation. The doses used were 3, 10, and 30 mg/kg, administered intraperitoneally. They acted through mechanisms that involve modulating mediators such as histamine, serotonin, PGE2, and bradykinin, and diminishing vascular permeability and neutrophil migration to the affected site.

The polysaccharide fraction can lead to decreased formation of pro-inflammatory cytokines such as TNF-α, IL-1β, and IL-6, and significantly reduce the activity of COX-2 and iNOS, thus reducing oxidative stress during acute inflammation.

4.3 Antimicrobial Mechanisms

The antimicrobial effect of T. occidentalis is thought to be due to the high concentration of α- and β-thujone, the main biologically active compounds in various essential oils that possess similar antimicrobial properties.

4.4 Thujone's Neuropharmacological Mechanism

Both α- and β-thujone inhibit GABA_A receptor-mediated responses. Thujone is a known neurotoxin that acts as a GABA receptor antagonist in the central nervous system. This mechanism underlies both the toxic potential of thujone at high doses and its observed convulsant properties in animals.

4.5 Anticancer Mechanisms (Preclinical)

In research on HPV-infected cervical cancer cells, the apoptotic cascade followed a caspase-3-dependent pathway supported by PARP-1 cleavage, while autophagic death was Beclin-1-dependent. Thujone, detected as the bioactive principle of Thuja mother tincture, showed anti-proliferative and anti-migratory potential at an IC₅₀ of 77 µg/mL. Molecular docking depicted thujone with the strongest affinity for mammalian target of rapamycin (mTOR), phosphoinositide 3-kinase, and protein kinase B, followed by B-cell lymphoma 2, murine double minute 2, and AMP-activated protein kinase, which might act as upstream triggers of apoptotic-autophagic crosstalk.

α-Thujone is the main component of Thuja occidentalis essential oil, which has been suggested to possess anti-tumor activities. This monoterpene easily penetrates the blood-brain barrier. Therefore, its effects were examined on the malignancy of glioblastoma multiforme (GBM) cells, with special emphasis on the mechanisms of its effects on cell viability and invasiveness.

5. Scientific Evidence by Area of Use

5.1 Upper Respiratory Tract Infections and Immunomodulation

The strongest body of clinical evidence for Thuja relates to its use in combination preparations for upper respiratory infections (URIs). The most studied formulation is Esberitox®, which combines Thuja occidentalis leaf tips with Echinacea purpurea, Echinacea pallida, and Baptisia tinctoria.

Using the combined preparation containing Echinacea root, wild indigo root, and white cedar leaf tips (Esberitox N), the efficacy and mode of action of a phytoimmunomodulator is described. Efficacy of the immunomodulator has been demonstrated in studies of acute viral respiratory tract infections and infections requiring antibiotic therapy. In a study compliant with GCP, the therapeutic superiority of the herbal immunomodulator over placebo was confirmed as statistically significant and clinically relevant.

A study was designed to verify the efficacy and safety of an herbal medication containing a mixture of Baptisiae tinctoriae radix, Echinaceae pallidae/purpureae radix, and Thujae occidentalis herba (SB-TOX) in the treatment of upper respiratory tract infections. A total of 91 adults (mean age 42.1 ± 13.0 years) were randomised to receive 19.2 mg of SB-TOX (n=31), 9.6 mg SB-TOX (n=29), or placebo (n=31) three times daily for 3–12 days. Since "running nose" is the main symptom of a common cold, the total number of facial tissues used throughout the clinical duration of their cold was the primary efficacy parameter.

A randomized, double-blind, placebo-controlled study showed a dose-dependent efficacy in the treatment of upper respiratory infections and, in particular, certain symptoms like rhinorrhea. Another study that enrolled 90 patients with acute rhinosinusitis compared Esberitox and doxycycline, Sinupret and doxycycline, and doxycycline alone, and found that both groups with combination therapies had a significantly higher rate of response. Reported adverse events included photosensitivity and gastrointestinal symptoms such as nausea.

Evidence assessment: Clinical studies of combination herbal products containing Thuja (e.g., Esberitox) show efficacy in treating upper respiratory infections, but controlled trials of Thuja alone are lacking. There is strong evidence available in the present literature advocating the potential use of T. occidentalis as an antiviral, immunostimulatory, or immunomodulatory agent. However, in some cases, the immunomodulatory potential of T. occidentalis alone has been considered less effective and can be improved if it is provided in a complex formulation. Evidence is therefore rated as moderate for the combination product and preliminary for Thuja as a monotherapy.

5.2 Warts, Condylomas, and HPV-Related Lesions

T. occidentalis has been used in the treatment of warts, papillomas, and condylomas caused by human papilloma virus (HPV). Thuja occidentalis is also active against enveloped viruses as well as naked viruses, such as the wart virus and enteroviruses.

A randomized clinical trial with 110 patients found both external (mother tincture) and internal (centesimal and LM potencies) Thuja treatments led to significant improvement in wart cases, with no significant difference between the two methods. A double-blind study compared Thuja occidentalis tablets alone versus tablets plus tincture. Both groups showed improvement in wart surface area over three months, with no significant difference between the two approaches.

A case report published in PMC describes Thuja occidentalis used to treat warts in the homeopathic system of medicine in a 34-year-old male who underwent a living donor renal transplantation. Resistant warts on the fingers were healed using an extract from T. occidentalis, which only caused superficial scarring to appear.

A case report demonstrates the use of Thuja in the management of laryngeal papillomatosis in an 8-year-old child, highlighting its immunopharmacological and antiviral potential.

A study noted the "multi-targeting" anticancer potential of Thuja and thujone for HPV-infected cervical cancer, and sought to determine if the homeopathic mother tincture and its bioactive component could combat HPV-16-infected SiHa cervical cancer cells, since it is globally acclaimed for HPV-mediated warts.

Evidence assessment: Thuja occidentalis is frequently cited as a key remedy in homeopathic practice for warts, often selected based on individual patient characteristics. Its use is supported by traditional and clinical experience, though high-quality, large-scale randomized controlled trials are limited. The in vitro and some small clinical data are encouraging but the overall evidence remains preliminary to moderate.

5.3 Anticancer Activity

Crude ethanolic extract of Thuja occidentalis (family: Cupressaceae) is used as homeopathic mother tincture (TOΦ) to treat various ailments, particularly moles and tumors. Anti-proliferative and apoptosis-inducing properties of TOΦ and the thujone-rich fraction (TRF) were evaluated for anti-cancer potential in the malignant melanoma cell line A375. Both TOΦ and TRF showed maximum cytotoxic effect on A375 cells, while other principal fractions had negligible or no such effect.

The level of antitumor factors such as IL-2 and TIMP was elevated by treatment with T. occidentalis and TPS in the serum, which was lowered in untreated tumor-bearing animals. This study clearly suggests that T. occidentalis and TPS effectively stimulate cell-mediated immune system and decrease pro-inflammatory cytokines, thereby inhibiting metastasis of tumor cells.

Protective effect of T. occidentalis has also been reported against radiation-induced toxicity in mice.

Evidence assessment: All anticancer evidence to date is derived from in vitro and animal studies. Despite wide medicinal applications of Thuja occidentalis, still little is known on its therapeutic potential in tumor treatment. No controlled human clinical trials have been conducted to establish anticancer efficacy; this area remains highly preliminary.

5.4 Polycystic Ovary Syndrome (PCOS)

A study concluded that T. occidentalis essential oil and its active component, α-thujone, can be used for the treatment of PCOS without inducing osteoporosis. The plasma low-density lipoprotein-cholesterol (LDL-C), leptin, and glucose concentrations were also significantly decreased in the T. occidentalis and α-thujone groups when compared to the control group. According to the phytochemical analyses, 25 compounds were identified in the T. occidentalis oil. The main constituents of the oil were the monoterpene ketones α- and β-thujone, fenchone, and sabinene, as well as the diterpenes beyerene and rimuene.

Evidence assessment: This evidence is from animal models only. Animal studies suggest benefits in diabetic neuropathy and nephropathy, polycystic ovary syndrome, and urinary tract infections. Evidence is preclinical only.

5.5 Antimicrobial Activity

The present work provides an overview about the state-of-the-art in pharmacological properties of T. occidentalis, including antioxidant, anti-inflammatory, antibacterial, antifungal, anticancer, antiviral, protective activity of the gastrointestinal tract, radioprotection, antipyretic, and lipid metabolism regulatory activity.

The major constituent of the oil, the monoterpene thujone, is used pharmacologically as an active ingredient in the production of nasal decongestants and cough suppressants.

Evidence assessment: Antimicrobial activity has been demonstrated in numerous in vitro studies. Translation to confirmed clinical outcomes in humans has primarily occurred through combination products such as Esberitox rather than Thuja alone. This remains an area of active preclinical investigation.

5.6 Urinary Tract Infections

A recent placebo-controlled trial found Thuja occidentalis 200CH significantly more effective than placebo for urinary tract infections. This refers to a homeopathic potency study. The overall body of evidence for urinary tract indications is very limited, consisting primarily of one small trial and historical use.

6. Body Systems and Health Areas Associated with Thuja

• Immune System: Immunostimulation, macrophage activation, T-lymphocyte proliferation, cytokine induction (primary area of evidence via combination products)
• Respiratory System: URI adjunct therapy, bronchial catarrh, sinusitis, angina (combination phytotherapy)
• Dermatological/Skin: Warts, condylomas, papillomas, psoriasis, eczema, skin tags (topical and internal homeopathic preparations)
• Urogenital System: Cystitis, enuresis, urinary tract infections, amenorrhea (traditional, limited clinical)
• Musculoskeletal: Rheumatism, arthritis (traditional use)
• Oncological (Preclinical): Antitumor, anti-proliferative, anti-metastatic activities in vitro and in animal models
• Reproductive: PCOS (animal model only)
• Gastrointestinal: Antidiarrheal, hepatoprotective, antiulcerative (preclinical)
• Metabolic: Lipid-lowering, antidiabetic (preclinical)

7. Dosage Forms and Reported Dosages

Dosages differ substantially between traditional/phytotherapeutic preparations and homeopathic dilutions.

7.1 Traditional Phytotherapy

In traditional phytotherapy, recommended oral doses of the drug consisting of dried young twigs are, for instance, 1 to 2 g, corresponding to up to 40 to 80 mg thujone, 3 times a day. Reported adverse effects include gastrointestinal disorders and vomiting.

7.2 Combination Phytotherapeutic Product (Esberitox)

In a randomized controlled trial evaluating an herbal medication containing Baptisiae tinctoriae radix, Echinaceae pallidae/purpureae radix, and Thujae occidentalis herba, a total of 91 adults were randomised to receive 19.2 mg of SB-TOX (n=31), 9.6 mg SB-TOX (n=29), or placebo (n=31) three times daily for 3–12 days. The doses refer to the extract combination rather than Thuja alone.

7.3 Homeopathic Preparations

One labelled homeopathic preparation (Thuja occidentalis 30C HPUS) instructs: adults and children should dissolve 5 pellets under the tongue 2 times a day, mornings and evenings, until wart is removed or as directed by a doctor.

For a liquid homeopathic tincture preparation, unless otherwise prescribed, adults take 15–20 drops, 3 times per day.

The homeopathic Thuja occidentalis mother tincture and the 1:10 dilution, when ingested orally, should be taken together with water due to the strong irritant properties to mucous membranes.

7.4 Topical Application

For labeled topical preparations, apply 3 times daily to affected area. Warts will dry and flake away over a 3–6 week period. Thuja occidentalis components in the HPUS are officially monographed in the Homeopathic Pharmacopeia of the United States.

Exposure to thujone at low dosages (3–7 mg/day) may be safe, but higher doses may be harmful.

8. Safety Considerations and Known Toxicity

8.1 Thujone Neurotoxicity

Due to the presence of the neurotoxic compound thujone, internal use can be harmful if used for prolonged periods or while pregnant. The primary concern regarding Thuja occidentalis centers on the presence of the volatile compound thujone, which is found in high concentrations in the crude plant and its essential oil. Thujone is a known neurotoxin that acts as a GABA receptor antagonist in the central nervous system.

If consumed internally, thujone can be neurotoxic, convulsant, and hallucinogenic. Long-term or excessive use of thujone-rich products can cause restlessness, vomiting, vertigo, tremors, renal damage, and convulsions. Internal use of Thuja decoctions and even very small doses of Thuja oil (e.g., 20 drops per day for 5 days) as an abortifacient has been associated with neurotoxicity, convulsions, and death.

A mixture of α- and β-thujone was convulsant and neurotoxic when administered intraperitoneally to rats. Subcutaneous thujone was convulsant but not lethal in mice at 590 mg/kg, and in rats at 36 mg/kg, but convulsant and lethal in rats above 0.2 mL/kg.

Repeated intake of thujone-containing beverages (e.g., absinthe) was reported to cause permanent disorders of the central nervous system.

8.2 Regulatory Status of Thujone

Thujone is the monoterpene found in the composition of many plants including Thuja occidentalis. However, the use of this compound is regulated by the European Parliament and Council and the European Medicines Agency. It was not possible from available information to establish a complete pharmacological and toxicological profile including NOELs and an ADI (acceptable daily intake) for Thuja occidentalis and its constituents.

8.3 Documented Adverse Events

Ingesting Thuja essential oil or large quantities of crude herbal material can lead to severe adverse effects, including painful diarrhea, vomiting, and nervous system toxicity. High doses of thujone can trigger convulsions and seizures, and in extreme cases, ingestion has resulted in death.

There is one report of Thuja oil causing convulsions. A 50-year-old woman ingested 20 drops twice a day for 5 days. In the pediatric setting, Stafstrom (2007) documented seizures in a 7-month-old child after exposure to the essential plant oil Thuja (Pediatr Neurol 2007;37:446–8).

8.4 Contraindications

• Thuja is absolutely contraindicated for use in pregnancy, as it is associated with a substantial risk of inducing fetal malformation.
• The use of mother tincture and the 1:10 dilution in pregnancy is contraindicated.
• Thuja might cause the immune system to become more active, which could increase the symptoms of autoimmune diseases such as multiple sclerosis (MS), lupus, and rheumatoid arthritis. If one has these conditions, it is best to avoid using Thuja.
• Taking Thuja might cause seizures in some people. Individuals with a history of seizures should not take Thuja.

8.5 Drug Interactions

Thujone's GABA-A antagonism could reduce efficacy of anticonvulsants; bornyl acetate may potentiate NSAIDs, raising bleeding concerns in sensitive individuals. Potential interactions have been noted in case reports for CNS stimulants and MAO inhibitors.

Individuals with autoimmune conditions such as multiple sclerosis or lupus should avoid internal use, as Thuja may stimulate immune activity and potentially worsen symptoms.

8.6 Skin Safety (Topical)

Undiluted Thuja oil can cause contact dermatitis, redness, and blisters if used at concentrations over 5%.

8.7 Note on Homeopathic Dilutions

Homeopathic Thuja occidentalis products have not been evaluated by the Food and Drug Administration for safety or efficacy, and the FDA is not aware of scientific evidence to support homeopathy as effective. At highly diluted homeopathic potencies (e.g., 30C, 200C), no detectable thujone would be present by standard chemical analysis, meaning the toxicological concerns described above apply specifically to low-dilution tinctures and herbal preparations rather than potentised homeopathic forms.

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