Why Linalool and Limonene Keep Showing Up on Soap Labels

If you make soap with lavender, citrus, or basically any essential oil blend, you have probably already met linalool and limonene without knowing their names. They are the two allergens that turn up most often, because they occur naturally in a huge range of oils that soap makers reach for constantly: lavender, bergamot, sweet orange, lemon, tea tree, pretty much anything citrusy or floral carries one or both.

That is why these two get singled out so often in conversations about fragrance allergen disclosure. Not because they are unusually dangerous, but because they are unusually common.

Where they actually come from

Linalool is a terpene alcohol found in lavender, coriander, and many mint-family plants. Limonene is what gives citrus peel its smell, and it is the dominant component in cold-pressed orange and lemon oils. Neither is added on purpose as "linalool" or "limonene" in most handmade soap. They arrive as part of the essential oil or fragrance oil you bought, sitting there as a natural constituent of a more complex blend.

That matters for filing purposes. When you notify a product, you are not just listing "Lavender Oil." Depending on the market's requirements, you may need to identify the specific allergenic constituents within that oil and their concentration in the finished bar.

The threshold logic

In Canada, disclosure of fragrance allergens hinges on concentration thresholds that differ by product type:

• Leave-on products: disclosure required above 0.001% (10 ppm)
• Rinse-off products: disclosure required above 0.01% (100 ppm)

Soap is rinse-off, so the bar is a bit higher than it would be for a lotion or a leave-on facial oil. But essential oils are potent, and a soap scented at even a modest percentage can easily push individual allergens like linalool or limonene past that 100 ppm line once you do the math on what fraction of the essential oil they actually make up.

Two dates matter here. List 1, the original fragrance allergen set, becomes mandatory on the Cosmetic Notification Form and the label on April 12, 2026. List 2, an expanded set aligned with international lists, becomes mandatory August 1, 2026. Linalool and limonene are both on List 1, so if you are filing or relabeling now, they are already on your radar.

Doing the math on a real bar

Say you scent a cold-process soap at 3% fragrance load using a lavender essential oil, and that oil is documented by the supplier as containing roughly 30% linalool. Multiply it through:

Step	Value
Essential oil in formula	3%
Linalool content of that oil	30%
Linalool in finished soap	0.9% (9,000 ppm)

That is far above the 100 ppm rinse-off threshold, so it needs to be disclosed. This is the same multiply-through logic you use for any supplier blend: take the component percentage inside the blend, multiply by how much of the blend you used, and that gives you the real concentration in the finished product.

Where to find your numbers

You cannot guess these percentages. You need a certificate of analysis or a technical data sheet from your essential oil or fragrance oil supplier that breaks down the allergen content. Reputable suppliers selling into regulated markets increasingly provide this by default, because they know soap makers need it. If yours does not, ask, or consider switching to one that does.

Keep that documentation on file even beyond what you disclose on the label. If a regulator or a customer asks how you arrived at a number, "the supplier's data sheet says so" is your answer, and you want it in writing.

What actually goes on the label and the filing

Once you know an allergen crosses the threshold, it gets listed by its INCI name (Linalool and Limonene are both standard INCI names, no translation needed) alongside your other ingredients, generally near the end of the list where trace constituents live. On the Cosmetic Notification Form itself, you list it the same way you would any other ingredient, by INCI name with its concentration or concentration range.

If you are running multiple scent variants of the same soap base, each variant may need its own look at allergen math, since a rose geranium bar and a peppermint bar carry completely different allergen profiles even if the base recipe is identical.

This is exactly the kind of ingredient-by-ingredient math that is easy to get wrong by hand, especially once you are juggling several essential oil blends across a product line. Cosmetic Comply runs each ingredient through its INCI and CAS mapping, carries the percentages through, and flags where you are sitting relative to these thresholds before you file, so you are not doing the multiplication on a napkin between batches.