If your candle smells of tonka bean, fresh hay or a warm almond-vanilla, it almost certainly contains coumarin. It's one of the oldest and best-loved molecules in perfumery, and it has a reputation: banned in food, linked to liver damage, flagged as an allergen. Most of that is true, but only part of it matters for a candle. Here's what coumarin is, what ECHA actually records for it, and how it changes your candle's label at a normal fragrance load.

What coumarin smells like, and where it comes from

Coumarin (CAS 91-64-5, EC 202-086-7) smells sweet, warm and hay-like, with an almond and vanilla edge. It's a white crystalline solid, so perfumers dissolve it into the rest of the oil. Nature makes plenty of it:

  • Tonka beans (Dipteryx odorata) usually contain 1 to 3% coumarin. The name comes from coumarou, the French word for the tonka tree.
  • Sweet woodruff and sweet clover release it as they dry, which is where the smell of fresh-cut hay comes from.
  • Cassia cinnamon is the main source in most people's diet. Ceylon cinnamon contains far less.

It was first isolated from tonka beans in 1820, and William Henry Perkin synthesised it in 1868. In 1882 Paul Parquet used synthetic coumarin in Houbigant's Fougère Royale, the first perfume built around a synthetic ingredient and the one that named the whole fougère family. Almost every "tonka", "hay" and many "vanilla" or "barbershop" candle oils still lean on it.

What ECHA records for coumarin

We checked ECHA's substance database and Classification & Labelling Inventory on 29 September 2026. Coumarin has no harmonised classification in CLP Annex VI. Instead, industry has notified 28 distinct self-classifications, and ECHA's prominent one (used by the large majority of notifiers) is:

  • Acute Tox. 4 (oral), H302 "Harmful if swallowed".
  • Skin Sens. 1, H317 "May cause an allergic skin reaction".
  • Aquatic Chronic 3, H412 "Harmful to aquatic life with long lasting effects".

That gives pure coumarin the exclamation mark pictogram and the signal word "Warning". No specific concentration limit is notified, so the generic CLP limits apply. Note that the sensitiser entry is plain Category 1, not 1A or 1B. If you want to know why that matters, we explain the difference between Skin Sens. 1A and 1B separately.

Coumarin is also one of the original 26 fragrance allergens that EU cosmetics law requires to be named on labels, and it stays on the allergen list behind the EUH208 line. The IFRA Standard restricts it for dermal sensitisation and systemic toxicity, with limits as low as 1.5% in fine fragrance (Category 4) and 1.6% in air freshener sprays (Category 10B), but 33% in candles (Category 12). See how IFRA categories work if those numbers are new to you. At any realistic load, a candle can't come close to 33%.

The liver story, in proportion

Coumarin's bad reputation comes from food. High doses damage the liver in animals, and a small number of sensitive people have developed liver problems after taking large amounts, often from supplements. The European Food Safety Authority set a tolerable daily intake of 0.1 mg per kg of body weight, confirmed in 2008, and EU flavourings law caps coumarin in foods, for example at 50 mg/kg in traditional cinnamon bakery. The usual worry is someone eating lots of cassia cinnamon every day.

All of that is about swallowing coumarin, day after day. A candle isn't eaten. The H302 on pure coumarin describes swallowing the raw material, and as the example below shows, it doesn't survive dilution into a candle anyway. The warning that does matter for candles is the one about skin: handling the wax or the fragrance oil. One more myth worth dropping: coumarin is not a blood thinner. Warfarin descends from dicoumarol, a different molecule formed in mouldy sweet clover.

A worked example: a tonka and vanilla candle

Take a hypothetical tonka-vanilla fragrance oil whose SDS lists 12% coumarin and 10% vanillin, used at a 10% load. Each hazard class follows its own rule:

  • Skin sensitisation. The candle holds 1.2% coumarin. For a Skin Sens. 1 substance the limit is 1%, so the candle is H317, with the exclamation mark, "Warning", and coumarin named on the label as the substance responsible.
  • Acute oral toxicity. CLP uses an acute toxicity estimate. When only an ingredient's category is known, a Category 4 substance counts with a converted estimate of 500 mg/kg, and a mixture only becomes Category 4 when its estimate drops to 2,000 mg/kg or less. That takes 25% coumarin in the mixture. At 1.2% the candle is nowhere near, and even this 12% oil on its own doesn't reach H302.
  • Aquatic hazard. Aquatic Chronic 3 ingredients need to add up to 25% before a mixture gets H412, so coumarin alone never gets a candle there. It only contributes to the sum with other aquatic ingredients.
  • Vanillin. Its prominent self-classification is Eye Irrit. 2, which needs 10% in the mixture. At 1% it adds nothing. We cover it in vanillin in candles.

Now drop the load to 8%. The candle holds 0.96% coumarin, just under 1%. The H317, the pictogram and the signal word all disappear. Coumarin doesn't vanish from the label, though: anything from 0.1% up still needs the EUH208 line, "Contains coumarin. May produce an allergic reaction." With this oil, that line stays down to a load of under 1%, so in practice every candle made with it carries it.

What to do with this

  • Find coumarin's exact percentage in Section 3 of your oil's SDS. Its concentration times your load decides between H317 and a simple EUH208 line, and the tipping point is often within a couple of points of load.
  • Don't copy H302 from the oil or from coumarin's own entry. It belongs to the swallowed raw material, not to a diluted candle.
  • Keep the liver story out of your marketing, both ways. Don't scare customers with it, and don't claim a tonka candle is "coumarin-free" if the oil says otherwise.

Molekule reads each component from your fragrance's SDS, checks it against ECHA's live classifications and runs these rules for your finished candle, including the load at which coumarin tips from EUH208 into H317. Check your tonka candle's label in Molekule.