The following article is used with the written permission of the author, Gillian Willis, pharmacist and toxicologist.

Tea Tree (Melaleuca) Oil

Tea tree oil (melaleuca oil) is being marketed for the treatment of  many disorders in humans and in animals. The active ingredients in  tea tree oil have a similar structure and action as turpentine.

Melaleuca oil comes from the Australian tea tree (Melaleuca  alternifolia). It is also known as tea tree oil and Australian tea  tree oil. The oil is reputed to have mild antibacterial and  antifungal properties and is marketed as a natural remedy in both  veterinary and human medicine.

Animals and humans are getting poisoned from topical use and from accidental ingestion of tea tree oil. I have numerous reports on file of toxic reactions from tea tree oil being used topically to treat fleas in animals, and  one case of avian poisoning. Melaleuca oil is highly lipophilic and can be absorbed through intact skin to cause systemic toxicity. Pets grooming themselves may also ingest some topically applied oil.

The owner of a lovebird applied one drop of tea tree oil to a bleeding blood feather of her lovebird. Within 10 minutes the bird  collapsed and was on the bottom of the cage. The bird was rushed to  the vet. Fortunately, with intensive care treatment, the bird recovered uneventfully.

Application of tea tree oil to control fleas has resulted in death in kittens.

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The following are abstracts  from the veterinary and medical literature:

. Villar D, Knight MJ, Hansen SR, Buck WB. Toxicity of melaleuca oil and related essential oils applied topically on dogs and cats. Vet Human Toxicol. 1994;36(2):139-142.

Abstract: "Cases of melaleuca oil toxiosis have been reported by veterinarians to the National Animal Poison Control Center (NAPCC) when the oil was appled dermally to dogs and cats. In most cases, the oil was used to treat dermatologic conditions at inappropriate high doses. The typical signs observed were depression, weakness, incoordination and muscle tremors. The active ingredients of commercial melaleuca oil are predominantly cyclic terpenes. Treatment of clinical signs and supportive care has been sufficient to achieve recovery without sequelae within 2-3 days."

"Toxicity: The most common clinical signs reported to the Animal Poison Control Center by veterinarians with adverse reactions in dogs and cats after dermal exposure of melaleuca oil include ataxia, incoordination, weakness, tremors, behavioral disorders and depression. The acute toxcicity (rabbit dermal LD 50 and rat oral LC 50) for the major terpenic compounds (linalool, ocimene, alpha-terpinene, 1,8-cineole, terpinolene, camphene) ranges between 2 and 5 g/kg body weight, which is considered a moderately toxic range.  From a toxicologic standpoint melaleuca oil can be compared to oil of turpentine, which is readily absorbed from the gastrointestinal tract and skin.

The highly lipophilic nature of melaleuca oil not only potentiates its antiseptic properties on the skno, but also its dermal absorption, which may account for the episodes reported to the NAPCC.

Treatment of Exposures: There is no specific antidote for the adverse reactions caused by dermal overexposure to melaleuca oil and related essential oils. Basic supportive care shoule include monitoring respiratory and cardiovascular functions as well as for checking for possible hypothermia; heat support should be provided as needed. For topical exposures resulting in toxicosis, a bath with mild non-insecticidal shampoo is recommended to remove residual amounts of the oil from skin and prevent further absorption. Intravenous fluids and glucose should strenthen the animal, overcome hypotension, and aid renal elimination."

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. Jacobs MR, Hornfeldt. Melaleuca oil poisoning. Clinical Toxicology 1994;32:461-464.

Abstract: "A 23-month-old boy became confused and was unable to walk thirty minutes after ingesting less than 10 mL of T36-C7, a commercial product that contained 100% melaleuca oil. The child was referred to a nearby hospital. His condition improved and he was asymptomatic within 5 hours of ingestion. He was discharged home the next day. Melaleuca oil, extracted from the Melaleuca alternifolia, contains 50-60% terpenes and related alcohols. This case report suggests that ingestion of a modest amount of a concentrated form of this oil may produce signs of toxicity."

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. Del Beccaro MA. Melaleuca oil poisoning in a 17-month-old. Vet Human Toxicol 1995;37:557-8.

Abstract: "Ingestion of significant quantities of melaleuca oil or Australian tea tree oil has been described only once in the medical literature. This report describes a 17-month-old male who ingested less than 10 mL of the oil and developed ataxia and drowsiness. Emergency physicians, poison control personnel and pediatricians should be aware of potential toxicity from this product."

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. Elliott C. Tea tree oil poisoning. Med J Australia 1993;159:830-831.

A 60-year-old male ingested 0.5 teaspoonful of tea tree oil and developed a dramatic rash, malaise and neutrophil leucocytosis.

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. Seawright A. Tea tree oil: comment. Med J Australia 1993;159:831.

This author commented that some tea tree oils contain a high concentration of 1,8-cineol (eucalyptol, cajeputol). Toxicity similar to that of eucalyptus oil would be expected. Toxic does of eucalyptus oil range from 5-30 mL in humans, with symptoms including respiratory depression, coma and death.

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. deGroot AC, Weyland JW. Systemic contact dermatitis from tea tree oil. Contact Dermatitis 1992;27:279-280.

This report in a human showed that this reaction was caused by the allergin, cineol present in the tea tree oil.

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CONCLUSION: One should be aware that that tea tree oil (melaleuca oil) is potentially toxic to animals and avians when applied topically.  Use this information and your own judgment when deciding if you feel comfortable in applying tea tree (melaleuca) oil to your pets. Tea tree oil should NOT be applied to avians.

Gillian Willis
Vancouver, B.C.