9 Tea Tree Oil Side Effects And Drug Interactions + Right Dosage

Reviewed by Madhu Sharma, Registered Dietitian
Written by Ravi Teja Tadimalla

Tea tree oil is quite popular in aromatherapy. Although most of its benefits are yet to be established, it has been used widely for its medicinal properties. However, research has revealed certain undesirable effects of tea tree oil.

Depending on how you use it, tea tree oil may trigger adverse effects in certain individuals. In this post, we will discuss the safety of tea tree oil according to research.

Tea Tree Oil – A Brief

Tea tree oil is also known as melaleuca oil.it is an essential oil with a fresh camphor-like odor and an appearance that ranges from pale yellow to colorless. It is taken from the leaves of the Melaleuca alternifolia plant and is native to Australia.

The oil, though toxic if taken orally, is used in cosmetics and skin creams in lower concentrations. Tea tree oil has also been claimed to treat numerous medical conditions, with most of the claims being proven. It is most effective as an antimicrobial agent and helps treat various dermatological issues like acne, lice, dandruff, etc.

However, there are certain concerns with respect to their safety.

Is Tea Tree Oil Safe?

Tea tree has been found to be poisonous if taken internally. Since it is a refined composition of numerous naturally occurring chemicals, its misuse might be hazardous.

According to an Australian study, the ill effects of tea tree oil can be minimized by avoiding ingestion. Using diluted oil for topical applications and using only the oil that has been stored properly can further help reduce the risk of side effects (1).

Though tea tree oil is possibly safe when applied to the skin, it might cause allergic contact dermatitis in certain individuals (2). As per anecdotal evidence, the oil can also cause swelling, skin irritation or itching, and skin dryness.

Tea tree oil is likely unsafe if taken orally. It might cause confusion, unsteadiness, inability to walk, and, in severe cases, coma. However, these effects are yet to be backed by solid research.

In the following section, we will explore the side effects of tea tree oil more elaborately.

Tea Tree Oil Side Effects

1. May Cause Allergies

Allergic reactions to tea tree oil can range from mild skin inflammation to severe rashes (3). Though it can be used (without much apprehension) by people who are not allergic to it, caution must be exercised while using it in general.

Anecdotal evidence suggests that using tea tree oil on dry or broken skin may cause skin irritation. The symptoms may include stinging, itching that burns, and mild to serious inflammation. Hence, doing a patch test before applying it is recommended.

Also, being allergic to cloves, guava, or eucalyptus may make one more susceptible to develop allergies with tea tree oil. The longer the tea tree oil has been allowed to age, the more likely it is to cause allergies.

Some anecdotal evidence also suggests that tea tree oil may cause sinus congestion, anaphylaxis, cramps, swelling, flushing, nausea, and lightheadedness.

According to one study, though most tea tree oil allergies are caused by the application of the pure oil itself, the cosmetics that contain tea tree oil could also be the culprits in certain cases (4). 

2. May Lead To A Bad Aftertaste

In a UAE study involving mouthwashes (one containing tea tree oil and the other containing a compound called cetylpyridinium chloride, or CPC), the CPC mouthwash was found to have a better antigingivitis effect. Tea tree oil had also induced a bitter aftertaste in one individual (5). The study concludes by stating that more research is needed to understand the antiplaque properties of tea tree oil.

In another study, the ingestion of tea tree oil by a 4-year-old had lead to unresponsiveness. Hence, tea tree oil must not be ingested by children (6).

3. May Cause Hormonal Side Effects

Tea tree oil was found to cause breast growth in adolescent boys. Tea tree oil might act as a potential endocrine disruptor and cause this to happen. According to a report published by The New England Journal of Medicine, gynecomastia (enlargement of a man’s breasts due to hormonal imbalance) was resolved in most cases post the discontinuation of the use of tea tree oil (7).

Similar findings were published in a report by the National Institutes of Health (8).

4. May Cause Diarrhea

One of the negative effects of tea tree oil is diarrhea. Ingestion of tea tree oil can cause diarrhea in certain cases. This can happen as a case of a severe allergic reaction to tea tree oil (9).

5. May Cause Ear Damage

If applied undiluted to mucous membranes, tea tree oil may cause discomfort and swelling. If it is being used to treat ear infections (which tea tree oil is often used for), it is always best to mix it with a carrier oil. A carrier oil like almond or olive oil, in combination with diluted tea tree oil, can be placed in the ear canal to treat related infections.

Practice caution when you are treating ear infections on your own at home. It is best to visit your doctor.

One good way to use tea tree oil (and avoid the troubles) is to dilute a few drops of the oil with a one-fourth cup of warm olive oil. Tilt your head to one side and pour a few drops into the infected ear with a dropper. Keep your head tilted for about a minute to allow the liquid to travel through your ear canal.

However, certain studies suggest not using tea tree oil in the ear as it might cause damage to the inner ear (10).

6. May Cause Muscle Tremors

Tea tree oil was found to cause a lack of muscle coordination upon ingestion. We strongly recommend not ingesting tea tree oil (3).

7. May Cause Skin Irritation And Other Skin Issues

Even as you use tea tree oil topically, it is important to monitor for any worsening skin conditions. Applying the oil to the skin can also cause burning and redness (11).

Some believe the tea tree could be harsh on sensitive skin. Anyone susceptible to eczema must use tea tree oil with extreme caution, though there is insufficient information in this regard.

It is always better to purchase tea tree oil that is already in the required dilution rather than mixing it yourself. You can also use alternatives like rosemary, lavender, or manuka oils on your skin – as these are gentler but equally effective.

Tea tree oil can also penetrate the outer layers of the skin, thereby increasing the chances of toxicity due to dermal absorption. This toxicity is dose-dependent, and most of the issues can be avoided by using the oil in its diluted form (12).

8. May Cause Depressive Behavior

Though depressive behavior hasn’t been observed in humans yet, related symptoms and signs of toxicity were noted in dogs and cats following the external application of the oil in high doses (13).

Tea tree oil can also cause excessive drowsiness if ingested (13).

Insufficient Evidence For The Following

9. May Cause Scalp Problems

Though tea tree oil is believed to treat scalp issues like dandruff, more research is needed to substantiate its beneficial uses (14). The oil is also likely to cause scalp allergies in some people, though we have only anecdotal evidence in this regard.

Those were tea tree oil side effects. When used topically, it might be safe in certain cases. But ingesting it can lead to tea tree oil poisoning, causing severe side effects.

Tea tree oil is also often recommended for treating nasal polyps, but some speculate it can also cause side effects. The oil may cause your nose to run, and it might even burn or sting. The polyp might swell before it shrinks.

Tea tree oil may also lead to mouth inflammation or mouth ulcers. However, we need more research to understand this phenomenon.

Certain side effects of tea tree oil are yet to be established. Hence, you should take precautions before using the oil. Also, consult your doctor.

One way of possibly mitigating the side effects is knowing the dosage of the oil.

What Is The Right Dosage Of Tea Tree Oil?

What happens if you use too much tea tree oil? There is no specific dosage of tea tree oil that has been specified. However, there are some guidelines.

If you are using tea tree oil for

  • Dental plaque – Use 2.5 % tea tree oil to brush your teeth daily for eight weeks.
  • Acne –Apply 5% tea tree oil as a gel to the skin once every day for three months.
  • Dandruff – Apply 5% tea tree oil shampoo to the scalp for three minutes daily for four weeks.
  • Eye infections– 50% tea tree oil is to be used as a weekly eyelid scrub for six weeks.
  • Skin allergies – 20% to 100% tea tree oil can be applied to the affected areas.
  • Vaginal infections – 20% tea tree oil can be applied for 24 hours using a soaked tampon.

Remember, never take tea tree oil orally.

Safety During Pregnancy Or Breastfeeding

There is insufficient data to support the safety of tea tree oil during pregnancy. Some anecdotal evidence suggests that using tea tree oil during labor can lead to the cessation of contractions of the uterus, which might put the baby and the mother at risk (this may happen if the uterus is exposed to tea tree oil). However, research is limited in this aspect.

There is no data indicating the excretion of tea tree oil components into breast milk (15). Neither is there any data on the safety of tea tree oil for nursing mothers or infants. The topical tea tree oil application is usually well tolerated. But it must never be taken orally.

Interactions With Drugs And Herbal Supplements

Tea tree oil must be used with caution when combined with antibiotics (13).


When used topically, tea tree oil can offer certain benefits. Otherwise, it may cause harm. Ensure you use the oil as per the recommended dosage to enjoy its benefits and to avoid the side effects to the extent possible. More importantly, consult your doctor before using tea tree oil.


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Ravi Teja Tadimalla is an editor and a published author. He graduated from SRM University, Chennai, and has been in the digital media field for over six years. He has a Professional Certificate in Food, Nutrition & Research from Wageningen University. He considers himself a sculptor born to chip away at content and reveal its dormant splendor. He started his career as a research writer, primarily focusing on health and wellness, and has over 250 articles to his credit. Ravi believes in the great possibilities of abundant health with natural foods and organic supplements. Reading and theater are his other interests.