Tea Tree Oil (Melaleuca Alternifolia): Notifying an Essential Oil

Tea tree oil shows up in soap bars, acne spot treatments, scalp serums, and a dozen other product types, and it's one of those essential oils where the INCI filing is genuinely simple but the claims conversation around it gets complicated fast. Let's separate the two.

The basics: INCI and CAS

Tea tree oil's INCI name is Melaleuca Alternifolia (Tea Tree) Leaf Oil, reflecting the botanical source name in Latin binomial format, which is standard for essential oils and plant extracts under the INCI system. Its CAS number is commonly listed as 68647-73-4, though essential oils can sometimes carry more than one CAS number depending on extraction method and how the substance is characterized, so it's worth confirming the number against your specific supplier's documentation rather than assuming a single figure applies universally.

Terpinen-4-ol and why the "quality" of tea tree oil varies

Tea tree oil isn't a single fixed chemical, it's a complex mixture of terpenes, and the compound most associated with its beneficial properties is terpinen-4-ol. International standards for tea tree oil typically specify a minimum terpinen-4-ol content alongside a maximum for 1,8-cineole, the component more associated with skin irritation. This matters for two reasons:

• Batch-to-batch variation is real. Tea tree oil from different regions, harvests, and distillation methods can vary meaningfully in its terpinen-4-ol and cineole ratios. A supplier's certificate of analysis should state these figures for the specific lot you're using.
• It affects formulation decisions, not just filing. Higher cineole content is generally associated with more irritation potential, so some formulators specifically source oil that meets a recognized quality standard rather than treating all tea tree oil as interchangeable.

None of this changes the INCI name or how you file it. Melaleuca Alternifolia Leaf Oil is the entry regardless of terpinen-4-ol content, but it's worth knowing your supplier's assay in case questions ever come up about formulation choices.

Hotlist considerations

Tea tree oil itself is a widely used essential oil, but it's worth checking the current Cosmetic Ingredient Hotlist for any restrictions tied to specific terpene components or concentration caps that may apply depending on how the oil is characterized and used. Essential oils in general are an area where Hotlist entries can be tied to a specific constituent rather than the whole oil, so don't assume that because "tea tree oil" isn't itself flagged, every component within it is automatically clear. This is exactly the kind of detail worth verifying against the current Hotlist at the time you file, since restricted-substance lists get updated.

The allergen angle

Like most essential oils, tea tree oil naturally contains some of the compounds on Canada's fragrance allergen lists, notably Limonene, which is a common constituent of many essential oils including tea tree. Depending on your finished concentration and whether it clears the leave-on (0.001%) or rinse-off (0.01%) threshold, Limonene may need its own line on your ingredient list and CNF once List 1 becomes mandatory on April 12, 2026. Check your supplier's assay for the actual Limonene percentage in your specific lot rather than assuming a textbook average, since natural variation is significant.

Where the real risk lives: claims, not filing

Here's the part that trips people up more than the INCI or CAS ever does. Tea tree oil has a reputation, deserved or not in the eyes of any given regulator, for antimicrobial and anti-acne properties, and it's extremely tempting to lean into that in your marketing copy. The problem is that antimicrobial and anti-acne claims are drug claims, not cosmetic claims. A soap that simply lists tea tree oil as an ingredient and makes a cleansing claim is a cosmetic. The moment you claim it treats acne, kills bacteria, or clears blemishes, you've stepped into drug territory, and that changes what regulatory pathway applies entirely, potentially requiring drug-level substantiation you almost certainly don't have.

Safe framing usually stays descriptive and sensory rather than therapeutic:

• "Formulated with tea tree oil" or "with Melaleuca Alternifolia Leaf Oil" describes the ingredient without claiming an outcome.
• "Refreshing, herbaceous scent" describes what the customer experiences.
• Avoid "clears acne," "kills bacteria," "treats blemishes," or anything implying the product changes a medical condition.

This distinction, cosmetic ingredient versus drug claim, is worth reviewing with fresh eyes on your actual label copy, because it's astonishingly easy to slide from "contains tea tree oil" to "fights breakouts" in a single product description without noticing the line you just crossed.

Filing it in practice

For the Cosmetic Notification Form itself, tea tree oil is not a complicated ingredient to declare, Melaleuca Alternifolia Leaf Oil at its concentration or range, screened against the current Hotlist, with any triggered allergen components (typically Limonene) declared separately if they clear the threshold. Cosmetic Comply maps the INCI and CAS automatically from your supplier information, checks the Hotlist, and calculates whether any natural allergen constituents clear the label threshold, so the ingredient side of a tea tree formula is usually one of the faster ones to get through review. The claims review on your packaging copy is the part worth spending your own time double-checking, since no ingredient database can catch a drug claim sitting in your marketing headline.