Citral and Eugenol Allergen Thresholds in Scented Products

Citral and eugenol tend to show up in totally different corners of a maker's shelf. Citral is the sharp, lemony compound found heavily in lemongrass and lemon myrtle oils. Eugenol is the warm, spicy note that makes clove smell like clove, and it's a major component of clove bud oil and shows up in smaller amounts in cinnamon and bay. They rarely appear in the same product, but they're worth pairing in one conversation because they illustrate the same underlying rule from two different angles.

The rule is the same, the sourcing habits are different

Both citral and eugenol are recognized fragrance allergens that require label and Cosmetic Notification Form disclosure once their concentration in the finished product crosses the relevant threshold: above 0.001% (10 ppm) in leave-on products, above 0.01% (100 ppm) in rinse-off products. Neither compound gets special treatment relative to the others on the list. What differs is how easily makers overlook them, because of where each one tends to hide.

Citral: the "it's just lemongrass" trap

Citral is often the dominant compound in lemongrass and lemon myrtle essential oils, sometimes making up a large share of the oil by weight. Makers using these oils for their bright, natural citrus scent often don't think of them as "fragrance allergen" territory the way a synthetic fragrance compound might read, since the ingredient list just says "Cymbopogon Citratus Oil" or similar, not "citral."

That's exactly the gap. The finished-product concentration is what matters, not how natural or single-source the oil feels. If a diffuser blend, soap, or lotion uses even a modest percentage of lemongrass oil, the calculation below often lands well above the leave-on threshold:

Component	Value
Citral share of lemongrass oil	commonly 70 to 85%
Oil use level in a soap, for example	1%
Resulting citral concentration	roughly 0.7 to 0.85%

That figure is dramatically above the 0.01% rinse-off threshold even for a wash-off product, which is why lemongrass-scented soaps and shampoos are one of the more reliable examples of "you almost certainly need to declare this."

Eugenol: the small-percentage surprise

Eugenol behaves a little differently. Clove bud oil is a very concentrated eugenol source, but clove-forward blends tend to be used at much lower percentages than a citrus oil, because the scent is potent and a little goes a long way. That lower use level can make the math feel like it should net out to "probably fine," but the leave-on threshold is genuinely tiny, and it's worth actually doing the calculation rather than trusting intuition:

Component	Value
Eugenol share of clove bud oil	commonly 70 to 90%
Oil use level in a leave-on balm, for example	0.3%
Resulting eugenol concentration	roughly 0.21 to 0.27%

Even at a use level that feels conservative, eugenol from clove oil routinely clears the disclosure threshold by a wide margin. The lesson isn't "clove oil is dangerous," it's that potent, low-dose essential oils are just as likely to trigger disclosure as high-dose ones, sometimes more so.

What to actually do with this

1. Identify which essential oils in your formula are known to carry significant citral or eugenol content, lemongrass, lemon myrtle, and melissa for citral, clove bud, clove leaf, cinnamon bark, and bay for eugenol are the common ones.
2. Get the actual percentage from your supplier's current documentation rather than a generalized reference figure, natural variation between crops and harvests is real.
3. Multiply by your use level to get finished-product concentration.
4. Compare against the leave-on or rinse-off threshold depending on your product category.
5. If you're over threshold, plan for label and CNF disclosure ahead of the relevant mandatory date, List 1 allergens become mandatory April 12, 2026, and the expanded List 2 set becomes mandatory August 1, 2026.

Don't let "natural" formulas skip this step

The instinct to treat essential-oil-based formulas as automatically simpler from a compliance standpoint is understandable and wrong. Synthetic fragrance compounds usually come with a tidy allergen declaration from the fragrance house. Essential oils require you to do more of that work yourself, pulling the constituent data and running the math. Cosmetic Comply's ingredient screening is built around exactly this gap, flagging essential oils with known allergen constituents like citral and eugenol so the threshold calculation happens as part of your filing rather than as a step you have to remember on your own.