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Overview: Thuja (Thuja occidentalis) is a type of cypress tree. Its leaves and twigs are used to make thuja oil, which is applied to the skin. Thuja is also found in some homeopathic products that are taken by mouth. These products are used for various purposes, but their benefits are not well defined. Common side effects of applying thuja oil to your skin include rash and irritation. Homeopathic thuja products are unlikely to cause side effects, but taking pure thuja or thuja oil by mouth may cause seizures. Before using thuja, tell your health care provider about any health conditions you have or medicines you are taking.

Uses

What is thuja used for?

Thuja (Thuja occidentalis) oil is applied to the skin for many reasons. Thuja is also an ingredient in some homeopathic products that are taken by mouth. However, the benefits of thuja for any use are not well defined.

Note: Thuja (thujone-free) is generally recognized as safe (GRAS) by the FDA for use as a food flavoring. Learn more about GRAS status here. The FDA has not reviewed other thuja products for safety and effectiveness. Learn more about homeopathic products here. Learn more about essential oils here.

How does thuja work (mechanism of action)?

Thuja (Thuja occidentalis) is a type of cypress tree. Its fresh leaves (needles) and twigs are used as a flavoring agent, to make essential oils, and as an ingredient in homeopathic products. Thuja is also sometimes referred to as cedar leaf or white cedar.

Thuja essential oil is made by heating up the leaves and twigs until certain chemicals, called volatile aromatic compounds, are released. This oil is applied to the skin for various purposes, including as an insect repellent and to help with warts. But it is not clear if or how it may work for any of these uses. Thuja oils should only be applied to the skin. They may be unsafe when taken by mouth (see Warnings & Precautions for more information).

Most other products that contain thuja are homeopathic. Homeopathic products are very dilute, which means they contain very small amounts of each ingredient. Sometimes, these amounts are so small that there may not be any thuja in the product at all. The very small amounts of thuja found in homeopathic products are unlikely to cause serious side effects. But it is not clear if or how they may work for any use.

Herbal products, such as thuja, naturally contain many different chemicals. The amounts of each chemical in a specific thuja product may vary. Some, none, or all of these chemicals may have effects on the body. These effects may change depending on how much of each chemical is found in the product you are using. 

How should I store thuja?

You should store thuja according to the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of thuja?

Homeopathic thuja products seem to be well tolerated. But thuja contains a chemical called thujone that may cause seizures when taken at high doses. See Warnings & Precautions for more information.

The most common side effects of applying thuja to the skin are rash and irritation. These side effects may vary depending on the dose or the specific product you are using. Tell your health care provider if you have any of these side effects that bother you.

There may be other side effects of thuja that are not listed here. Contact your health care provider if you think you are having a side effect from a natural substance. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of thuja?

While less common, the most serious side effects of thuja are described below, along with what to do if they happen.

Severe Allergic Reactions. Thuja may cause allergic reactions, which can be serious. Stop using thuja and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Seizures. A chemical in thuja, called thujone, can cause seizures. This is more likely to happen with higher doses of thujone (see Warnings & Precautions to learn more). There are many types of seizures, and some of them are not easy to recognize. Stop taking thuja and call your health care provider if you have any of the following signs that a seizure is happening or could happen.

  • Muscle twitching, jerking, spasms, tremors, or other uncontrolled movements
  • Stiffening of your arms and legs
  • Feeling anxious, nervous, confused, or a sense of dread
  • Feeling dizzy or lightheaded
  • Falling or losing consciousness

Warnings & Precautions

Who should not use thuja?

Allergies to Ingredients. People who are allergic to any of the following should not use thuja.

  • Cedar leaf oil
  • Thuja
  • Thuja occidentalis
  • Thujone
  • White cedar
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific thuja products they stock.

What should I know about thuja before using it?

Thuja is used as a flavoring agent. It is also available as a homeopathic product and an essential oil that can be applied to the skin. It cannot be marketed to treat or cure a disease.

Keep thuja out of the reach of children.

Thuja contains thujone, a chemical that can cause seizures when used in large amounts. In the U.S., thuja flavoring agents are required to be thujone-free. But thuja essential oils may still contain thujone. These oils are meant to be applied to the skin and should not be taken by mouth. Read and follow the directions on the specific product you are using, or use it as recommended by your health care provider.

Many products that contain thuja are homeopathic, meaning they contain only very small amounts of each ingredient. These small amounts are unlikely to cause serious side effects when taken by mouth. But some homeopathic products have been found to contain larger amounts than listed on the label. These large amounts can cause serious side effects. The FDA has not tested thuja products to confirm that they contain the ingredients or amounts stated on their labels. Learn more about the risks of homeopathic products here.

Herbal products, such as thuja, naturally contain many different chemicals. The amount of each chemical in a specific thuja product can change for many reasons, including the area where the tree was grown, the weather during growth, the time of year when it was harvested, and the way that it was processed after it was harvested. If you switch to a new bottle or a different brand, you may not have the same effects or side effects because of this variability. Talk to your health care provider if you have questions or concerns.

What should I tell my health care provider before using thuja?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if thuja is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Kidney or liver problems
  • Seizures
  • Sensitive skin

Pregnancy. It is not known if or how thuja could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. It is not known if thuja passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. 

Interactions

Does thuja interact with foods or drinks?

There are no known interactions between thuja and foods or drinks.

It is unknown if drinking alcohol will affect thuja.

Does thuja interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

The interactions between thuja and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with thuja is incomplete. Always check with your health care provider before taking thuja with any medicines.

Overdose/Missed Dose

What should I do if I accidentally use too much thuja?

If you or someone else has used too much thuja, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

Thuja is available as a flavoring agent, as an essential oil, and in homeopathic products. Some thuja products should only be applied to the skin and should not be taken by mouth. Read the product label closely, and speak with a health care provider about how to use thuja safely.