Natural Health Products

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General Information

Thuja is a type of evergreen tree that is native to eastern North America. The aerialaerialplant parts appearing above ground (above ground) parts of the tree are used in herbal medicine. The leaves of the thuja tree contain an active ingredient called thujone.

Common Name(s)
thuja, arborvitae, cedar leaf oil
Scientific Name(s)
Thuja occidentalis L. (Cupressaceae)
How is this product usually used?

Thuja can be taken orallyorallyto be taken by mouth (swallowed) (by mouth) or used topicallytopicallyto be applied on the skin on the skin.  It comes in the form of dried leaves, infusioninfusionthe process of steeping or soaking plant material in hot or cold water to isolate its active ingredient, tincturetincturea desired active ingredient that is extracted from alcoholic solution, or liquid extractextractto get, separate, or isolate a desired active ingredient.

When taken orally, the recommended amount is 1 g to 2 g of dried aerialaerialplant parts appearing above ground parts, 3 times a day. It is prepared by pouring 250 mL of boiling water over dried leaves, then steepsteepTo soak an agent (such as tea) to extract its active ingredienting for 10 to 15 minutes. Oral thuja is meant for occasional use only.

When used topically on the skin, the usual dose of thuja ranges from 0.1 g to 2 g of dried aerial parts, 3 times a day. Apply the liquid or tincture to affected area(s).

Your health care provider may have recommended using this product in other ways. Contact a health care provider if you have questions.

What is this product used for?

Oral thuja is traditionally used in herbal medicine as an expectorantexpectorantan agent that thins mucus (phlegm) so that it can be absorbed or coughed up (a medication that helps clear mucusmucusa moist and sticky substance produced by the mucous membranes from the airways).

Topical thuja is used in traditional herbal medicine to remove warts on the hands and feet or to help treat fungal infections (e.g., ringworm).

Thuja has been used for many other conditions, including bronchitis, coughs, bacterial and viral infections (e.g., strep throat, herpes simplex virus), muscle pain, osteoarthritis, and trigeminal neuralgia (chronic and severe pain affecting a large nerve in the head). It can also be used as a diureticdiuretican agent that increases urine flow (increases urination) and to induce abortions.

However, thuja has not been shown to effectively treat the conditions it has been used for and additional studies are needed to confirm its benefits.

Your health care provider may have recommended this product for other conditions. Contact a health care provider if you have questions.

What else should I be aware of?

Although thuja appears to be safe when used in small amounts that are sometimes found in foods (it is sometimes used as a flavouring agent), it may not be safe to use as a medication or supplement, since very little is known about it.

Large doses of thuja have caused side effects such as nausea, vomiting, diarrhea, gut irritation, and bleeding from membranes lining the body (e.g., the skin lining the inside of the mouth). There have also been reports of asthma attack, liver and kidney damage, seizures, and death from taking more than the recommended amount of thuja.

Do not use thuja if you have gastrointestinal problems such as intestinal ulcers and stomach inflammation.

If the symptoms being treated with thuja persist or become worse, consult a health care provider.

Do not use thuja if you are pregnant. See your doctor first before using thuja if you are breast-feeding.

Thuja leaves contain an oil called thujone, which may cause convulsions, liver and kidney damage, muscle spasms, and hallucinations if taken orallyorallyto be taken by mouth (swallowed). If you are taking other herbs or natural products that have thujone, talk to your health care provider before using thuja. Herbs that may contain thujone include:

  • juniper
  • mugwort
  • oak moss
  • oriental arborvitae
  • sage
  • tansy
  • tree moss
  • wormwood

See your doctor if you have diabetes or poor blood circulation before applying thuja on the skin.

Do not take thuja if you have epilepsy or are taking anticonvulsant medications (i.e., medication that prevents seizures).

Do not take thuja if you are taking medications that may lower your seizure threshold (i.e., medications that increase your risk of having a seizure). Medications that can lower the seizure threshold include:

  • anesthetics
  • antiarrhythmicantiarrhythmican agent to treat irregular heartbeats
  • antibiotics (e.g., ciprofloxacin)
  • antidepressants (e.g., bupropion)
  • antihistamines (e.g., diphenhydramine)
  • antipsychotics (e.g., clozapine)
  • immunosuppressants (e.g., tacrolimus)
  • narcotics (e.g., tramadol)
  • stimulants (i.e., substances that have a stimulating effect, like cocaine)
  • theophylline

Before taking any new medications, including natural health products, speak to your physician, pharmacist, or other health care provider. Tell your health care provider about any natural health products you may be taking.

  1. American Cancer Society. Complementary and Alternative Medicine. Thuja. [updated 2008 November 28; cited2014 July 03]. Available from:
  2. Health Canada. Natural Health Products Ingredients Database. Thuja-Oral. [updated 2008 April 25; cited 2014 July 3]. Available from:
  3. Health Canada. Natural Health Products Ingredients Database. Thuja-Topical. [updated 2014 March 24; cited 2014 July 3]. Available from:
  4. National Institutes of Health. Autoimmune Diseases. [updated 2010 September 22; cited 2011 September 7]. Available from:
  5. National Institute of Neurological Disorders and Stroke. Trigeminal Neuralgia Fact Sheet. [updated 2011 April 18; cited 2011 September 8]. Available from:
  6. Natural Database. Natural Medicines Comprehensive Database. Thuja. [updated 2011 September 6; cited 2011 September 7]. Available from:
  7. PubMed Health. AHFS Consumer Medication Information [internet]. Theophylline. [updated 2010 August 1; cited 2011 September 8]. Available from:


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