Turning a Fragrance Oil Load Into an Allergen Percent

Someone asked us last week why their 3% fragrance oil load produced a linalool number that seemed too small to matter, until it didn't. The answer is that allergen concentration isn't the fragrance load itself, it's a chain of two percentages multiplied together, and skipping that second multiplication is the single most common way makers underestimate what's actually in their bottle.

The chain you actually need

Your fragrance oil is not 100% allergen. It's a blend of dozens of aromatic compounds, and the allergens regulators care about (linalool, limonene, geraniol, and the rest) are usually a fraction of the total blend, not the whole thing. So there are two numbers you need, multiplied together, not just one:

1. Use rate: how much fragrance oil you put into the finished product, as a percentage of the total batch.
2. Allergen fraction: what percentage of that fragrance oil is made up of the specific named allergen, which your supplier's documentation should tell you.

The finished-product allergen concentration is:

Use rate × Allergen fraction = Allergen concentration in finished product

Walking through it

Say you're making a body lotion (a leave-on product) with a 2% fragrance oil load. Your supplier's allergen declaration says the fragrance oil contains 8% linalool by weight. The math is:

0.02 (use rate) × 0.08 (allergen fraction) = 0.0016, or 0.16% linalool in the finished lotion.

That 0.16% is way above the leave-on disclosure threshold of 0.001% (10 ppm). Linalool needs to be named on the label and the notification. This is the step people skip: they see "8% linalool in the fragrance oil" and think that number is what matters, when it's actually the use rate that has already diluted it down, and you still need to check the diluted number against threshold, not the raw supplier number.

Where people get tripped up

Mistake one: comparing the wrong number to the threshold. The 8% figure from the supplier is the allergen's share of the fragrance oil, not its share of your finished lotion. Compare the finished-product number to threshold, always, never the concentrate number.

Mistake two: forgetting rinse-off has a different, higher bar. The same math applies to shampoo or soap, but the disclosure threshold is 0.01% (100 ppm) instead of 0.001%, since rinse-off products have much shorter skin contact time. Run the same multiplication, then check it against the correct threshold for your product type.

Mistake three: assuming a low fragrance load means no disclosure. A 0.5% fragrance load sounds tiny. But if that fragrance oil is 15% limonene, a common situation for citrus-forward blends, the math still comes out to 0.075% limonene in the finished product, comfortably above even the rinse-off threshold. Low fragrance load doesn't automatically mean low allergen exposure if the allergen fraction inside that fragrance is high.

A reference table for the calculation

Fragrance use rate	Allergen fraction in fragrance	Allergen % in finished product	Leave-on disclosure (>0.001%)?	Rinse-off disclosure (>0.01%)?
0.5%	15% (limonene)	0.075%	Yes	Yes
1%	5% (geraniol)	0.05%	Yes	Yes
2%	8% (linalool)	0.16%	Yes	Yes
0.1%	2% (eugenol)	0.002%	Yes	No
0.05%	1% (coumarin)	0.0005%	No	No

That last row is worth sitting with. Even a very light fragrance touch can clear the leave-on threshold if the allergen fraction is high enough, and only drops below both thresholds once the use rate gets quite low.

Getting the allergen fraction in the first place

Your fragrance supplier should be able to provide an allergen declaration alongside the fragrance oil, listing each named allergen (from List 1 and eventually List 2) as a percentage of the blend. If they can't, ask, since this data is what your whole downstream calculation depends on. Without it, you're guessing, and guessing on an allergen threshold is not a great place to guess.

Building this into your workflow

Every fragrance-containing product in your line needs this chain run separately, for every named allergen in that particular fragrance oil, and separately again for leave-on versus rinse-off thresholds if you sell the same scent in more than one product type. It adds up fast across a catalog. Cosmetic Comply runs this two-step multiplication automatically once you enter your fragrance use rate and upload the supplier's allergen declaration, flagging every allergen that crosses threshold before it becomes a mislabeling problem down the line.