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Other common name(s): eastern white cedar, northern white cedar, yellow cedar, tree of life, arborvitae, swamp cedar

Scientific/medical name(s): Thuja occidentalis


Thuja (pronounced THOO-ya) is an evergreen in the cypress family, native to eastern North America. The tree is also grown in Europe as an ornamental plant. The parts used in herbal remedies are the branches and the tiny, flat, scale-like leaves, which contain the oil thujone.


Available scientific evidence does not support claims that thuja or its extract is safe or effective. Taken internally, the herb can cause serious side effects, and it may be toxic in large doses. The essential oil contained in the tree, also known as cedar leaf oil, is not generally sold for internal use. It is poisonous and can also irritate or burn skin and eyes.

How is it promoted for use?

Thuja is promoted as a treatment for many medical conditions, including cancer. Some proponents claim that thuja decreases the toxic effects of chemotherapy and radiation therapy. Herbalists prescribe thuja to treat viral and bacterial infections and coughs and other respiratory ailments, including strep throat and respiratory distress related to congestive heart failure. Herbalists also use it as a diuretic to increase urination, and as an astringent to "purify the blood," reduce inflammation, and cleanse the body of "toxins." Thuja is sometimes used with antibiotics to treat bacterial skin infections and herpes sores. It has even been used by some practitioners to induce abortions. Thuja ointment is applied to the skin for ailments such as psoriasis, eczema, vaginal infections, warts, muscle aches, and rheumatism.

Some practitioners of homeopathy (see Homeopathy) recommend use of very dilute thuja, in pill or liquid form, for treating irritability, depression, sadness, impaired thinking, headache, warts, growths, rashes, runny nose, sores in the nose, mouth pain, toothache, gas, hemorrhoids, watery stool, enlarged prostate, gonorrhea, back pain, joint pain, bad dreams, tiredness, insomnia, fevers, shaking chills, muscle pain, and cancer.

What does it involve?

Leaves from the tree are harvested and dried. Liquid extracts, tinctures, and tea made from thuja are taken internally. There is no standard dose of the herb. Thuja ointment is applied directly to the skin. Thuja oil and capsules are available in health food stores and over the Internet. When properly prepared and dosed as dietary supplements, the thujone levels are reportedly below the toxic range. However, because dietary supplements are not considered drugs, the US Food and Drug Administration (FDA) does not hold them to the same strict safety requirements that prescription drugs or over-the-counter drugs must meet.

Homeopathic dilutions of thuja are available to take by mouth, in pill or liquid form. Thuja is also made into homeopathic creams or ointments to be applied to the skin. These contain very tiny or even undectable amounts of thuja.

What is the history behind it?

Native Americans of the eastern United States and Canada used thuja for generations to treat menstrual problems, headaches, and heart ailments (see Native American Healing). Loggers drank tea made from white cedar twigs to relieve rheumatism. During the seventeenth century, some people called the eastern white cedar the "tree of life," because they believed that its sap had healing powers. In the late 1800s, the US Pharmacopoeia (the US compendium of quality control test and information on drugs) listed thuja as a treatment to stimulate the uterus and as a diuretic to increase urine flow.

Thujone (a major component of thuja oil) is banned as a food or drink additive in the United States, but small amounts are used in some alcoholic drinks in Europe. It is used in shoe polish and as a pest repellant. Cedar leaf oil, which is distilled from the leaves of Thuja occidentalis, is used in some furniture polishes and fragrances.

What is the evidence?

Human clinical trials of thuja by itself have not been reported. A 2005 German study looked at a mixture of extracts that included echinacea, baptisia, and thuja in the treatment of 91 adults with colds and runny noses. Those who received the extracts used fewer facial tissues than those who got placebo. However, it is impossible to say how much of this effect was related to thuja.

Available scientific evidence does not support claims that thuja is effective in treating cancer or any other disease. The medical literature contains no studies on the effects of thuja as an herbal remedy in humans, and there is very little scientific data to verify that the herb has any therapeutic value. Many supporters base their claims on limited laboratory experiments or individual reports. One laboratory study done in Germany found that a type of complex sugar called a polysaccharide from thuja enhanced the immune system's ability to fight off invading germs. However, even though laboratory studies may show the substance holds promise, further studies are needed to find out whether the results apply to humans.

Are there any possible problems or complications?

This substance may not have been thoroughly tested to find out how it interacts with medicines, foods, herbs, or supplements. Even though some reports of interactions and harmful effects may be published, full studies of interactions and effects are not often available. Because of these limitations, any information on ill effects and interactions below should be considered incomplete.

Because so little is known about thuja, it is not recommended for any medicinal use.

Taken internally, thuja can be toxic in large doses, although the exact amount that causes problems is uncertain. Some people who have consumed thuja reportedly experienced asthma attacks, intestinal irritation, excess stimulation of the nervous system, and spontaneous abortion (miscarriage).

The essential oil causes spasms if taken internally, and in high doses it can cause seizures as well as damage to the liver and the kidneys. The fresh leaves and shoots can also cause poisoning. Deaths have been reported. Skin or eye contact with cedar leaf oil can cause severe irritation or burns. Asthma and rashes have occurred in people who work with the wood of this tree.

Thujone, a component of thuja, is known to cause muscle spasms, seizures, and hallucinations if taken internally. These neurological toxicities are the results of thujone interfering with the action of gamma amino butyric acid, often known as GABA, on nerve cells in the brain. In high doses thujone is known to damage the liver and the kidneys. Thujone occurs in a number of other plants, most notably wormwood and mugwort (see Wormwood and Mugwort).

People with seizure disorders or gastrointestinal problems (such as ulcers or gastritis) should avoid thuja. Women who are pregnant or breast-feeding should not use this herb. Relying on this type of treatment alone and avoiding or delaying conventional medical care for cancer may have serious health consequences.

Additional resources

More information from your American Cancer Society

The following information on complementary and alternative therapies may also be helpful to you. These materials may be found on our Web site (www.cancer.org) or ordered from our toll-free number (1-800-ACS-2345).

Dietary Supplements: What Is Safe?

The ACS Operational Statement on Complementary and Alternative Methods of Cancer Management

Complementary and Alternative Methods and Cancer

Placebo Effect

Learning About New Ways to Treat Cancer

Learning About New Ways to Prevent Cancer


Native American Healing




Cartier A, Chan H, Malo JL, Pineau L, Tse KS, Chan-Yeung M. Occupational asthma caused by eastern white cedar (Thuja occidentalis) with demonstration that plicatic acid is present in this wood dust and is the causal agent. J Allergy Clin Immunol. 1986;77:639-645.

Deane PM. Conifer pollen sensitivity in western New York: cedar pollens. Allergy Asthma Proc. 2005;26:352-355.

Alpha-thujone (546-80-5). National Toxicology Program Web site. Accessed at http://ntp.niehs.nih.gov/index.cfm?objectid=03DB8C36-E7A1-9889-3BDF8436F2A8C51F on June 6, 2008.

Fetrow CW, Avila JR. Professional's Handbook of Complementary & Alternative Medicines. Philadelphia, PA: Lippincott Williams & Wilkins; 2004.

Gruenwald J. PDR for Herbal Medicines. 3rd ed. Montvale, NJ: Thomson PDR; 2004.

Material safety data sheet: cedar leaf oil. ScienceLab Web site. Accessed at www.sciencelab.com/xMSDS-Cedar_leaf_oil-9923339 on June 6, 2008.

Naser B, Lund B, Henneicke-von Zepelin HH, Köhler G, Lehmacher W, Scaglione F. A randomized, double-blind, placebo-controlled, clinical dose-response trial of an extract of Baptisia, Echinacea and Thuja for the treatment of patients with common cold. Phytomedicine. 2005;12:715-722.

Offergeld R, Reinecker C, Gumz E, et al. Mitogenic activity of high molecular polysaccharide fractions isolated from the cuppressaceae Thuja occidentalis L. enhanced cytokine-production by thyapolysaccharide, g-fraction (TPSg). Leukemia. 1992;3:189S-191S.

Note: This information may not cover all possible claims, uses, actions, precautions, side effects or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for consultation with your doctor, who is familiar with your medical situation.

Last Medical Review: 11/28/2008
Last Revised: 11/28/2008