Which Allergens Show Up on a Shampoo Label

Run the same essential oil blend through a leave-on serum and a rinse-off shampoo, and you'll get two completely different allergen disclosure lists out the other end. That's not a formulation quirk, it's the rinse-off threshold doing exactly what it's designed to do. Let's walk through an actual example.

The threshold difference, quickly

Canada's fragrance allergen disclosure trigger depends on whether a product is leave-on or rinse-off. Leave-on products, things that stay on skin or hair like lotions, serums, and leave-in conditioners, trigger disclosure above 0.001% (10 ppm). Rinse-off products, like shampoo, body wash, and bar soap, have a higher trigger of 0.01% (100 ppm), ten times higher than the leave-on threshold.

The reasoning makes sense once you think about exposure. A leave-on product sits on skin for hours, so even small concentrations of an allergen represent meaningful, sustained contact. A rinse-off product is on the scalp or skin for a few minutes before being washed away, so the same concentration represents far less actual exposure. Regulators set the disclosure bar accordingly.

A worked shampoo example

Say you're formulating a shampoo with a fragrance blend used at 0.8% of the total formula. The blend's supplier documentation shows the following allergen composition within that blend:

Allergen	Percent of fragrance blend	Use level of blend	Concentration in finished shampoo	Rinse-off threshold	Disclose?
Linalool	8%	0.8%	0.064% (640 ppm)	0.01% (100 ppm)	Yes
Limonene	5%	0.8%	0.04% (400 ppm)	0.01% (100 ppm)	Yes
Citronellol	0.6%	0.8%	0.0048% (48 ppm)	0.01% (100 ppm)	No
Geraniol	0.3%	0.8%	0.0024% (24 ppm)	0.01% (100 ppm)	No
Coumarin	0.1%	0.8%	0.0008% (8 ppm)	0.01% (100 ppm)	No

Run that exact same fragrance blend, at the exact same 0.8% use level, in a leave-on lotion instead, and compare it against the leave-on threshold of 0.001% (10 ppm):

Allergen	Concentration in finished lotion	Leave-on threshold	Disclose?
Linalool	0.064% (640 ppm)	0.001% (10 ppm)	Yes
Limonene	0.04% (400 ppm)	0.001% (10 ppm)	Yes
Citronellol	0.0048% (48 ppm)	0.001% (10 ppm)	Yes
Geraniol	0.0024% (24 ppm)	0.001% (10 ppm)	Yes
Coumarin	0.0008% (8 ppm)	0.001% (10 ppm)	No

Same blend, same use level, four allergens disclosed instead of two. That's the rinse-off threshold at work, and it's exactly why you can't reuse an allergen disclosure list across product types even when the fragrance is identical.

The math you actually need to do

The core calculation is always: allergen percentage within the blend, multiplied by the blend's use level in the finished product, equals the allergen's real concentration in what you're selling. Supplier documentation almost never hands you the finished-product concentration directly, it gives you the blend's internal composition, and you carry that through yourself based on how much of the blend you're using.

Skipping this step and assuming a supplier's "contains allergens above 1%" note tells you what to disclose is a common mistake. What matters is the allergen's concentration in your finished product, not its concentration inside the fragrance blend itself.

Why shampoo specifically deserves its own check

Shampoo formulas often carry a slightly higher fragrance load than leave-on products because the scent needs to survive dilution in water and rinsing without disappearing entirely. That higher fragrance percentage can offset some of the benefit of the rinse-off threshold, so don't assume rinse-off automatically means a short allergen list. Run the actual numbers for your specific formula rather than assuming.

Keep in mind too that these thresholds apply within the broader List 1 and List 2 allergen framework, with their own separate mandatory dates in 2026, so a shampoo compliant today may need its allergen disclosure expanded as those dates arrive and more allergens come into scope.

Carrying supplier blend percentages through to real finished-product concentrations, and checking each one against the correct leave-on or rinse-off threshold, is precisely the kind of repetitive, detail-heavy work Cosmetic Comply automates as part of screening your ingredient list before filing.