CAS Numbers for the Most Common Fragrance Allergens

Supplier documentation doesn't always use the same name twice. One fragrance house's allergen declaration sheet calls it "d-Limonene," another just says "Limonene," a GC/MS report might list it under a slightly different synonym entirely. The CAS number is what lets you confirm you're actually looking at the same substance across three different documents, which matters a lot once you're trying to total up an allergen's concentration from multiple ingredients that all happen to contain it.

Why the CAS number is your anchor point

INCI names are standardized for labeling, but supplier paperwork, GC/MS reports, and older safety data sheets sometimes use trade jargon, chemical synonyms, or regional naming conventions instead. If you're trying to confirm that the "Linalool" on your essential oil's composition report is the same substance you need to declare on your CNF, matching CAS numbers is the reliable way to do it, since a CAS number identifies one specific substance regardless of what name got printed on a given document.

A reference table

Here are CAS numbers for several of the fragrance allergens that come up constantly in Canada's disclosure framework. Always confirm against the current official list before filing, since exact numbering and any related synonyms are best verified at the source, but this is a solid starting reference for matching supplier data.

Allergen (INCI)	CAS number	Commonly found in
Limonene	5989-27-5	Citrus oils, many fragrance blends
Linalool	78-70-6	Lavender, bergamot, many florals
Citronellol	106-22-9	Rose, geranium, citronella oil
Geraniol	106-24-1	Rose, geranium, palmarosa
Eugenol	97-53-0	Clove, cinnamon leaf oil
Coumarin	91-64-5	Tonka bean, some synthetic fragrance bases

A word on multiple CAS numbers and no CAS numbers

Some substances have more than one CAS number in circulation, often because an older registration and a newer, more specific one both exist, or because isomers of the same compound (like d-Limonene versus l-Limonene) were registered separately before being treated as equivalent for regulatory purposes. If a supplier document gives you a CAS number that doesn't match the one you expected, don't assume it's an error, check whether it's a recognized alternate registration for the same substance before flagging it as a mismatch.

On the flip side, some botanical extracts genuinely have no CAS number, because they're complex, variable natural mixtures rather than single defined substances. This is different from the named allergens above, which are specific molecules and do have CAS identifiers. Don't confuse "this essential oil as a whole has no CAS number" with "the allergen constituents inside it have no CAS number." The oil itself might not carry one, but the specific allergen molecules you're testing for, Linalool, Geraniol, and so on, absolutely do.

Using this table in practice

When you're building your ingredient documentation, the workflow looks like this:

1. Pull the composition or allergen declaration report for each fragrance-containing ingredient, whether it's a synthetic compound or an essential oil.
2. Match each named constituent to its CAS number, using a reference table like the one above to catch synonym mismatches.
3. If the same allergen shows up across multiple ingredients in your formula, for example Limonene from both a citrus essential oil and a separate fragrance compound, add the concentrations together, since the disclosure threshold applies to the total amount of that allergen in the finished product, not to each source individually.
4. Compare the total against the leave-on (0.001%) or rinse-off (0.01%) threshold depending on your product type.

That third step is the one people skip most often, and it's a real gap, since two ingredients each contributing a small amount of Linalool can add up to a declarable total even if neither one alone would trip the threshold.

Keeping this current

Regulatory lists get amended, and CAS numbers occasionally get superseded or clarified, so treat any printed table, including this one, as a starting reference rather than a permanent record. Before a filing, it's worth a quick check against the current official source for anything you're relying on to make a disclosure decision.

If cross-referencing CAS numbers across a stack of supplier declarations sounds like the kind of detail work you'd rather hand off, Cosmetic Comply matches your ingredients to their INCI names and CAS numbers automatically, then screens the resulting list for allergen thresholds before a real reviewer signs off on the filing.