"Made with 100% pure essential oils, no nasty chemicals" is a common promise on handmade candles. It sells well, and it often comes with an assumption: a natural scent shouldn't need hazard warnings. EU law doesn't work that way. An essential oil is a chemical substance like any other, and in a candle it can put more on the label than a synthetic fragrance at the same load.

An essential oil is a substance, not an exemption

Under REACH and CLP, an essential oil is registered and classified as a single substance of a special kind: a UVCB (a substance of unknown or variable composition, complex reaction products or biological materials), also called a natural complex substance. Sweet orange oil, for example, sits in ECHA's database as "Orange, sweet, ext.", EC 232-433-8. It's one entry, but chemically it's a blend of dozens of molecules, and it's those molecules that carry the hazards.

Nothing in CLP treats "natural" differently when it comes to skin sensitisation, irritation or aquatic toxicity. Limonene from an orange peel is the same molecule as limonene from a chemical plant, and it's classified the same way.

What ECHA records for common essential oils

None of these oils has a harmonised EU classification. Their classification comes from the companies that place them on the market, and ECHA shows the most common one as the "prominent" entry. We checked ECHA's C&L Inventory on 29 September 2026:

  • Sweet orange oil (EC 232-433-8): Flam. Liq. 3, Asp. Tox. 1, Skin Irrit. 2, Skin Sens. 1, Aquatic Chronic 3. Signal word "Danger".
  • Lavender oil (Lavandula angustifolia, EC 289-995-2): Asp. Tox. 1, Skin Irrit. 2, Eye Irrit. 2, Skin Sens. 1B, Aquatic Chronic 3. "Danger".
  • Clove oil ("Clove, ext.", EC 284-638-7): Asp. Tox. 1, Skin Irrit. 2, Eye Irrit. 2, Skin Sens. 1. "Danger".
  • Tea tree oil (Melaleuca alternifolia, EC 285-377-1): Flam. Liq. 3, Acute Tox. 4 (oral and inhalation), Asp. Tox. 1, Skin Irrit. 2, Aquatic Chronic 2. "Danger".

The reason is the composition. Limonene makes up more than 85% of sweet orange oil, and limonene has a harmonised classification that includes Skin Sens. 1B, Asp. Tox. 1 and Aquatic Chronic 3. Lavender oil meeting the ISO 3515 standard contains 25 to 38% linalool, harmonised Skin Sens. 1B, and 25 to 45% linalyl acetate, which industry self-classifies as Skin Sens. 1B. Clove bud oil is mostly eugenol, another known fragrance allergen.

What changed in the 2024 CLP revision

The revised CLP Regulation, Regulation (EU) 2024/2865, added rules for "substances containing more than one constituent". For carcinogenicity, mutagenicity, reproductive toxicity and endocrine disruption, and for some environmental properties, these substances must be assessed using the data on each known constituent, much like a mixture.

Plant extracts were the most contested point. The final text says those rules don't apply to multi-constituent substances extracted from plants that aren't chemically modified. Essential oils are covered by that exemption, for now. The Commission must report on the question by 11 December 2029, possibly with a legislative proposal.

For a candle maker, that exemption matters less than it sounds. It covers those specific hazard classes, not skin sensitisation or irritation. And in your finished candle, the calculation you run is already constituent by constituent, because that's how fragrance SDSs list their composition.

A worked example: 10% essential oil vs a synthetic blend

Take three soy candles, each with a 10% fragrance load. The figures below are illustrative, using typical compositions:

  • 100% sweet orange oil. About 90% of the oil is limonene, so the candle holds roughly 9% limonene. That's nine times the 1% limit for a Skin Sens. 1B substance. The candle is classified H317 "May cause an allergic skin reaction", with the exclamation mark pictogram, the signal word "Warning", and limonene named on the label.
  • 100% lavender oil, at 35% linalool and 35% linalyl acetate. The candle holds 3.5% of each. Both are over 1%, so it's H317 with the exclamation mark again.
  • A synthetic orange blend whose SDS lists 5% limonene and 8% linalool. The candle holds 0.5% limonene and 0.8% linalool. Both are under 1%, so no H317 and no pictogram. Both are above 0.1%, so they go on the EUH208 line: "Contains d-limonene, linalool. May produce an allergic reaction."

Now try to bring the natural candles down to the synthetic's label. Orange oil would need a load of about 1.1% to keep limonene under 1%, which barely scents a candle. Lavender would need under about 2.8%. At any load a customer would notice, a pure orange or lavender candle carries the exclamation mark.

The rest of the SDS matters less than it looks. Asp. Tox. 1 drives the "Danger" on the oil's own sheet, but it only applies to liquids of low viscosity, so it doesn't carry through to a solid candle. Aquatic Chronic 3 needs 25% in the finished product to give H412 on its own, far above a 10% load. Tea tree oil is different: as an Aquatic Chronic 2 substance, 10% in the candle is enough for H412.

What to do with this

  • Get an SDS for every essential oil, with its composition. "Pure lavender oil" on the bottle tells you nothing about linalool content. Section 3 should list the main constituents and their ranges.
  • Don't market "natural" as "hazard-free". A label with H317 and a "chemical-free" claim beside it contradict each other, and the classification is the legally binding part.
  • If you want a lighter label, blend. Mixing a small share of essential oil into a well-documented fragrance often keeps the character without pushing a single constituent past its limit.

Molekule treats essential oils the way CLP does: it reads each constituent from the SDS, checks it against ECHA's live classifications, and calculates the finished label for your candle at your load. Check your essential-oil candle's label in Molekule.