No the Cineole is not a skin irritant.

Because of a few uncorroborated statements in the early 1981’s1 and 90’s2 that cineole is a skin irritant, “high”cineole tea tree oil (meaning that anything with more than 4%) has been regarded by much of the
market as inferior and even avoided.

Since the 1970’s numerous scientific studies demonstrated that the cineole content in tea tree oil is not contributory to any cases of skin irritation by tea tree oil. In 1997 leading scientists reported to the Australian Government a study titled “Why Cineole is not detrimental to tea tree oils”3. The report included details showing no human skin irritancy at levels up to 28% cineole (twice the specified maximum in the ISO and Australian standards). The report further includes appendices with complete copies of various supporting earlier scientific reports. [A complete report is free online – see reference at end of

In 2005, three of the world’s leading scientists in tea tree oil research conducted a rigorous search of the literature and toxicology databases and published their findings as a compilation of toxicity data4 for the 15 tea tree oil components specified in the ISO 4730. This work included specifically the scientific literature/databases review for 1,8-cineole skin irritancy. No scientific literature was cited that demonstrated any human skin irritancy by cineole. [A complete report is free online – see reference at end of document.] It is worth noting that eucalyptus oil (which is specified as a pharmaceutical ingredient at a minimum of 70% 1,8-cineole) is well known for its long and extensive usage in skin formulations. As with tea tree oil products and indeed any product, usage should be discontinued if sensitivity or allergy is observed.

Extensive studies have shown that generally there is an inverse relationship in tea tree oil between cineole and terpinen-4-ol concentration. Low cineole tea tree oil (<4%) generally has the highest concentration of terpinen-4-ol (>36%) in M. alternifolia. Terpinen-4-ol is responsible for much of tea tree oil’s biological activity. Therefore, the inference has been that higher cineole means lower bioactivity.

The inverse relationship between cineole and terpinen-4-ol is a generalised one derived from the analysis of thousands of tea tree oil samples. However, there are M. alternifolia chemotypes (plant variants) that have high concentrations of both components. Indeed MCNE’s special CinRich field has for many years consistently produced tea tree oil with >37% T-4-ol and 7-10% cineole. According to the general observation, a tea tree oil with 8% cineole could be predicted to have a T-4-ol concentration around 33%, however, a coincident high terpinen-4-ol, (as with CinRich), is certainly not inconsistent with the biogenetic pathways of monoterpenes in Melaleuca tea trees.

No, higher cineole levels doesn’t means lower bioactivity.

This has not been demonstrated – various studies over the last 20 years have shown that the cineole content (up to 20%) does not detract from the bioactivity of Australian tea tree oil where concentrations of terpinen-4-ol is greater than 30%6. Some studies have indicated that higher cineole contents in tea tree oil may enhance bioactivity particularly antifungal performance7. The increase overall percentage of oxy-terpenes associated with higher cineole oils (with high terpinen-4-ol content like CinRich) contributes to a greater overall water solubility of the oil which can contribute to relatively greater bio-activity8. Cineole has also been shown to be a (dermal) penetration enhancer

Low cineole content tea tree oil has been promoted as an implied requirement for the elevation of tea tree oil to “pharmaceutical” or “therapeutical” grade. This is simply deceptive –In no pharmacopoeia referring to tea tree oil/Melaleuca oil is reference made to low cineole indeed reference9 is made to the ISO 4730 and AS 2782 where cineole is specified to be a maximum of 15%.

The subjectivity of smell remains a cornerstone of the fragrance industry. Tea tree oil finds minimal use as a fragrance. Its smell is possibly best likened to a mild industrial solvent – pleasant to some, disagreeable to others. The variation of cineole content in tea tree oils between 2 and 10% is not readily discernable by the average human nose. Cineole “competes” with a range of terpenes of similar volatility and type of smell, none of which could be regarded as subtle. The overall smell of tea tree oil is predominated by the terpinen-4-ol smell.

Tea Tree Oil comprises a mixture of monoterpenes, sesquiterpenes and terpene alcohols. The main active component is Terpinen-4-ol, which is present at 39%-45% in MCNE TTO. Other active components include terpinolene, alpha alpha and gamma terpinene, terpineol and p-cymene. There are approximately 150 natural chemicals in Tea Tree oil.

While TTO has a mild natural aroma, impurities caused by poor agricultural ordistillation practice are responsible for sharp, sometimes acrid odours in poor quality TTO.

This is often accompanied by development of a yellow colouration. MCNE TTO has the mildest odour of TTO on the market. Reputable fragrance companies can produce fragrances to harmonize with the odour of tea tree oilinpersonal care products. Beware of two types of low odour TTO being offered on the market:

Deodorised TTO – this is normally heavily diluted with solvent.

Reodorised TTO – this is normally off specification TTO with cheap synthetic aroma chemicals added.

The concentration of TTO depends on several factors:
– desired effect (e.g. therapeutic or non therapeutic)
– formulation
– product positioning
Please contact us and we will be pleased to discuss the best way to optimize your product.

MCNE Tea Tree Oil is produced only on the Main Camp plantation in Northern NSW, Australia.

MCNE is the world leader in Tea Tree Oil and is the sole supplier of genuine Tea Tree Oil processed through a GMP specification built distillery.

MCNE plantation is certified to ISO 14001 (Environment Management Systems) and the production facility is certified ISO 9001 (Quality Systems). MCNE Tea Tree Oil has been extensively clinically tested to prove that it has very minor potential for skin irritancy or allergenicity and that it shows good anti-inflammatory effect. 

This is really two questions: one answer for bulk TTO, one answer for consumer products.

For bulk TTO: the only suitable packaging is in nitrogen-purged stainless steel drums.
Aluminium containers, Fluorinated Plastic containers and Epon Lined drums are only suitable for short term storage of less than 6 months.

For consumer products: due to the high solvency and penetrating nature of TTO care should be taken when choosing your packaging material. This is particularly important with plastics. As a general rule, low, medium and high-density polyethylene containers should be avoided, as the oil tends to migrate through the container resulting in bottle panelling and loss of TTO. The physical problems to some extent can be overcome by using thicker walled HDPE containers.

While glass and aluminium can be used for packaging neat tea tree oil, polypropylene, PVC, PET and some laminates can be used for TTO products containing up to 20% TTO.
Various treatments are available to provide barrier protection for packaging materials. Further advice on these treatments can be obtained by contacting us.

To avoid any undesirable packaging problems it is strongly recommended that stability work be carried out before launching a product in the market.

Toxicology studies conducted on behalf of ATTIA in the late 1980ʼs indicated that neat TTO has an oral LD50 in rats of 1700 mg/kg and may have some mild toxic effects if taken internally.

Products in which Tea Tree Oil has been successfully used in concentrations up to 1% include lip balm, mouthwashes and flavors, toothpaste, throat lozenges and treatment of cold sores.

The main active component of Tea Tree Oil is Terpinen-4-ol which is present at about 40%. As a guide, we would recommend that products containing Tea Tree Oil as an active maintain a mildly acidic to neutral pH in the range between 5.5-7. However, our research indicates little difference over the range 4-8.

Ti-tree is the common name for plants in the Cordyline genus.

These are found in New Zealand and the South Pacific

The international standard for TTO does not specify which species of Melaleuca must be used to produce the oil. It does however provide compositional limits for 15 of the more than 100 components that make up TTO. Most TTO is produced from Melaleuca alternifolia grown on plantations but other plants that may produce suitable oils include M. dissitiflora and M. linariifolia.

The native habitat of M alternifolia is a small area of north-eastern New South Wales, Australia. However, M. alternifolia has been cultivated successfully in other parts of New South Wales, in other states of Australia such as Queensland and Western Australia and in other countries.

The essential oils distilled from Kunzea ericoides and Leptospermum scoparium, also known as kanuka and manuka oils respectively, are often referred to as New Zealand Tea Tree oils. They are very different in composition from TTO and it cannot be assumed that they have the same medicinal properties as those shown for TTO.

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