Every autumn, cinnamon candles come back: apple and cinnamon, cinnamon and orange, "Christmas spice". They're also the candles most likely to come back from the label calculation with an exclamation mark, even at a modest fragrance load. The reason is one molecule, cinnamaldehyde. It's what cinnamon smells like, and EU law treats it as one of the strongest skin sensitisers in perfumery.

The molecule that is cinnamon

Cinnamaldehyde (3-phenylprop-2-enal, CAS 104-55-2, called cinnamal on ingredient lists) is the warm, sweet, spicy note you recognise as cinnamon bark. It isn't one note among many. It's the bulk of the oil:

  • Cassia oil (Cinnamomum cassia, the "Chinese cinnamon" of most supermarket spice) is dominated by cinnamaldehyde, with published analyses reporting up to around 90%.
  • Ceylon cinnamon bark oil (Cinnamomum verum) is also mostly cinnamaldehyde, typically in the 65 to 80% range in published analyses, with a little eugenol.
  • Cinnamon leaf oil, from the same Ceylon tree, flips the ratio. It's mostly eugenol, often 70 to 90%, which is why it smells closer to clove than to bark.

Cinnamon fragrance oils sold for candles usually rebuild this note from synthetic cinnamaldehyde, sometimes with a splash of cassia oil. Either way, if it smells like cinnamon bark, cinnamaldehyde is almost certainly in Section 3 of the safety data sheet.

How the EU classifies cinnamaldehyde

We checked ECHA's C&L Inventory on 29 September 2026. Cinnamaldehyde has a harmonised classification in CLP Annex VI, index number 606-155-00-6, added by the 21st adaptation to CLP (Delegated Regulation (EU) 2024/197, applying from 1 September 2025):

  • Skin Sens. 1A, H317 "May cause an allergic skin reaction", signal word "Warning".
  • A specific concentration limit of 0.01% for H317. The same entry covers the (2E) isomer, CAS 14371-10-9.

The harmonised entry only fixes skin sensitisation. For other hazards, suppliers still classify it themselves. In ECHA's notifications most companies also report skin irritation (H315), serious eye irritation (H319) and, in about three quarters of reports, harm in contact with skin (H312). Those matter for the neat oil. At candle concentrations they fall far below their limits, so the one that reaches your candle label is H317.

If you've read our explainer on skin sensitiser 1A vs 1B, you'll see why 0.01% is so striking. A 1B sensitiser like linalool classifies a mixture at 1%. A plain 1A substance at 0.1%. Cinnamaldehyde's limit is 100 times lower than linalool's.

Why IFRA says yes and CLP still says H317

IFRA restricts cinnamaldehyde because of dermal sensitisation. Under its standard (published in the 49th Amendment and carried into the 51st), fine fragrance is capped at 0.25% and many rinse-off and leave-on products lower still. But for Category 12, which covers products not intended for skin contact such as candles, wax melts and reed diffusers, the limit is "No Restriction". Sprayed room fragrances are a different category (10B), capped at 1.8% of the finished product. (More on how these groups work in IFRA categories explained.)

That's a safety assessment of use: a candle isn't meant to touch skin. CLP works differently. It classifies the product as a mixture, by the concentration of each hazardous ingredient in it, whatever the use. So a cinnamon candle can be fully IFRA compliant and still need the exclamation mark.

Cinnamyl alcohol, the relative

Cinnamyl alcohol (CAS 104-54-1) is a close relative with a softer, balsamic, hyacinth-like smell. It's common in the same spicy and floral accords, and like cinnamal it's on the EU's long-standing list of fragrance allergens named on cosmetics. It has no harmonised classification. ECHA's prominent industry entry lists Skin Sens. 1 (H317), Acute Tox. 4 oral (H302) and Aquatic Chronic 2 (H411). As a plain Category 1 sensitiser with no specific limit, it classifies your candle at 1%, a hundred times later than cinnamal. IFRA restricts it too, but allows up to 51% in Category 12.

A worked example: the holiday cinnamon candle

Take a hypothetical "Cinnamon & Orange" fragrance oil whose SDS lists 2% cinnamaldehyde. For cinnamaldehyde in the finished candle:

  • H317 and the exclamation mark from 0.01%.
  • EUH208 ("Contains cinnamal. May produce an allergic reaction.") from 0.001%, a tenth of its specific limit. See what the EUH208 line is.

Now run the loads:

  • 10% load: 2% × 10% = 0.2% cinnamaldehyde in the candle. That's 20 times the limit. H317, exclamation mark, "Warning".
  • 8% load: 0.16%. Still 16 times over. Same label.
  • How low to lose H317? Below 0.01% in the candle means a load under 0.5%. Nobody makes a scented candle that way.

The cinnamon note doesn't have to be the star, either. Suppose a gourmand "Vanilla Bakery" oil contains only 0.1% cinnamaldehyde for warmth:

  • At 10%, the candle holds exactly 0.01%. That reaches the limit: H317 with the exclamation mark.
  • At 8%, it's 0.008%. Below the limit, above 0.001%: no pictogram, but cinnamal goes on the EUH208 line.

Compare linalool. To reach its 1% limit at a 10% load, it has to make up 10% of the fragrance oil. Cinnamaldehyde does the same at 0.1%. That's why the spice candles in a Christmas range are usually the first to need a pictogram.

What to do with this

  • Look for cinnamal on every autumn and winter SDS, not just the ones named "cinnamon". It hides in gourmand, spice and "cosy" blends at small percentages.
  • Treat essential oils the same way. A few drops of cassia or cinnamon bark oil add a lot of cinnamaldehyde. Leaf oil adds less, but it brings a lot of eugenol, itself a listed fragrance allergen.
  • Don't expect to label your way out by trimming the load. For a true cinnamon scent, plan on H317 and design the label for it.

Molekule reads each component from your fragrance SDS, pulls its live ECHA classification and specific concentration limits, and shows the load at which your candle gains or loses H317. Check your cinnamon candle's label in Molekule.