Leave-On vs Rinse-Off: Which Allergen Threshold Applies

Here's a question that comes up constantly once makers start dealing with fragrance allergen disclosure: why does a rinse-off product get more room to breathe than a leave-on one, when they might use the exact same fragrance oil? The short answer is exposure time, but it's worth walking through the actual numbers, because the difference between the two thresholds is bigger than most people expect.

The two thresholds

Canada's fragrance allergen disclosure rules set different triggers depending on how a product is used:

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

That's a tenfold difference. A body lotion that stays on your skin all day is held to a threshold ten times stricter than a shampoo that's rinsed off in the shower a minute or two after application. The logic is straightforward: prolonged skin contact means more opportunity for a sensitized person to react, so the bar for disclosure is set lower.

Why the same fragrance dose behaves differently

Imagine you use the same fragrance oil, at the same dose, in two different products: a leave-on body butter and a rinse-off shampoo. If that fragrance oil naturally contains linalool at a level that works out to 0.05% in your finished product, here's what happens:

• In the body butter (leave-on), 0.05% is well above the 0.001% threshold, so linalool needs to be disclosed.
• In the shampoo (rinse-off), 0.05% is well below the 0.01% threshold... actually in this case it would still be above it, since 0.05% is greater than 0.01%. But drop the fragrance dose down, or dilute the same oil more in the rinse-off formula, and you can end up in a range like 0.005%, which clears the rinse-off threshold but would still trip the leave-on one.

That's the practical trap. A fragrance level that's perfectly fine to leave undisclosed in a rinse-off product can require full disclosure the moment you reuse the same fragrance oil in a leave-on version of the product line, even without changing the fragrance dose ratio much at all.

A worked comparison

Allergen level in finished product	Leave-on status	Rinse-off status
0.02% (200 ppm)	Disclose	Disclose
0.005% (50 ppm)	Disclose	Do not disclose
0.0005% (5 ppm)	Do not disclose	Do not disclose

The middle row is where most of the confusion lives. A concentration that clears a rinse-off product cleanly can still require disclosure the moment the same fragrance shows up in a leave-on formula.

Why this matters for a product line

A lot of small brands build a "family" of products around one signature scent: a lotion, a body wash, a solid perfume, maybe a hair oil. Because those products span both leave-on and rinse-off categories, you can't assume that clearing the allergen disclosure question for one product in the family clears it for all of them. Each finished product needs to be evaluated on its own, using the actual concentration of each allergen it contains and the correct threshold for how that specific product is used.

The mandatory dates to keep in mind

For Canada specifically, allergen disclosure is becoming mandatory in two waves. List 1, the original fragrance allergen set, becomes mandatory on both the Cosmetic Notification Form and the label on April 12, 2026. List 2, an expanded set aligned with international lists, follows on August 1, 2026. If you're formulating now, it's worth checking both lists against your fragrance suppliers' allergen breakdowns rather than only checking List 1 and assuming you're covered going forward.

Getting the actual numbers

None of this works without knowing what's actually in your fragrance oil. Fragrance suppliers should be able to provide an allergen declaration listing common sensitizers like limonene, linalool, citronellol, geraniol, coumarin, and eugenol, each at its percentage within the fragrance oil itself. From there, you multiply by your fragrance's use level in the finished product to get the real number to check against whichever threshold applies.

This is one of the areas where a bit of automation genuinely helps, since checking multiple allergens against two different thresholds across several related products in a line is tedious to do by hand and easy to get wrong once you're juggling more than two or three SKUs. Cosmetic Comply screens each ingredient, including fragrance allergens carried through from a blend, against the correct threshold for the product type you're filing, so a leave-on and a rinse-off version of the same scent get evaluated correctly rather than lumped together.