The Rinse-Off Allergen Threshold That Governs Soap

Ask a soap maker and a lotion maker about fragrance allergen disclosure and you'll get two different anxiety levels, and there's a real reason for that. The threshold that triggers mandatory disclosure is not the same for something you wash off as it is for something you leave on your skin, and soap sits on the easier side of that line.

The two numbers

Canada's fragrance allergen framework sets disclosure triggers at two different concentrations depending on how the product is used:

• Leave-on products: disclosure kicks in above 0.001%, which is 10 parts per million.
• Rinse-off products: disclosure kicks in above 0.01%, which is 100 parts per million.

That is a full order of magnitude of difference. A body lotion has to disclose an allergen at a tenth the concentration that a bar soap does, because the exposure logic behind the rule assumes rinse-off contact is brief and gets, well, rinsed off, while a leave-on product sits on skin for hours.

Why soap gets the benefit of the doubt

The reasoning is straightforward: contact time and residue matter enormously for skin sensitization risk. A leave-on moisturizer keeps trace fragrance compounds in contact with skin all day. A bar of soap contacts skin for the length of a shower and most of it goes down the drain. The regulatory framework reflects that difference directly in the threshold, not just in general guidance language.

For a soap maker working with essential oil blends, this means you have real headroom compared to a lotion maker using the identical oils. A fragrance load that would force disclosure in a face cream can sit comfortably below the line in a wash-off bar.

Where soap makers still get caught out

The higher threshold does not mean soap is exempt from thinking about this at all. A few ways soap makers still trip the rinse-off line or misjudge it:

• Concentrated fragrance oils. A heavily fragranced novelty soap, the kind sold as a solid perfume bar or a highly scented guest soap, can carry enough allergenic compounds to clear even the 100 ppm rinse-off threshold.
• Superfatted or "leave a film" bars. Some handmade soaps are formulated to leave moisturizing oils on skin deliberately. If a soap is marketed or used more like a leave-on treatment, the conservative move is to apply the leave-on threshold even if it is technically sold as a rinse-off bar.
• Multiple essential oils stacking the same allergen. Linalool shows up in lavender, bergamot, and many other oils. If your bar blends several oils that each contribute a little linalool, you add their contributions together before comparing to the threshold, not each one separately.
• Forgetting the blend expansion. A supplier's fragrance blend is not one substance. Each aromatic compound inside it, limonene, citronellol, geraniol, eugenol, coumarin, whatever it contains, needs its own concentration worked out before you know if any single one clears the line.

Timing to keep on your radar

In Canada, the allergen disclosure rules are rolling out in two phases. The first list of fragrance allergens becomes mandatory on the notification form and the label on April 12, 2026. A second, expanded list aligned with broader international allergen lists follows on August 1, 2026. If you are formulating soap now with an eye toward these dates, it is worth running your fragrance math against both lists rather than just the first one, since an ingredient that clears List 1 comfortably might still land on List 2.

A simple worked comparison

Product type	Threshold	50 g bar with 2% fragrance oil containing 3% linalool	Result
Rinse-off soap	0.01% (100 ppm)	2% × 3% = 0.06% linalool in finished bar	Above threshold, disclose
Leave-on lotion (same fragrance load)	0.001% (10 ppm)	Same 0.06%	Well above threshold, disclose

Notice that in this example both products end up disclosing, because 0.06% clears even the more forgiving rinse-off line. The threshold difference matters most in borderline cases, not in heavily fragranced ones.

True soap versus soap that makes a cosmetic claim

One more wrinkle worth remembering: a genuine "true soap," made from alkali salts of fatty acids and sold purely on a cleansing claim, can sit outside cosmetic regulation entirely in some markets. The moment you add a cosmetic-style claim, moisturizing, anti-acne, softening, gentle enough for sensitive skin, that bar becomes a cosmetic and the same allergen disclosure logic applies as it would to any other cosmetic product. A lot of handmade soap makers make this claim without realizing it changes their regulatory category.

Running the actual numbers on a fragrance blend by hand is tedious, especially once you are stacking three or four essential oils and trying to track every allergenic compound across all of them. Cosmetic Comply's ingredient matching does that expansion automatically, carrying each blend's components and percentages through so you can see, at a glance, whether your bar sits under the rinse-off line or needs disclosure.