Pet-safe candles: a chandler's guide to fragrance toxicity

Cats lack a key isoform of the liver enzyme glucuronyl transferase, which mammals use to clear phenolic and monoterpene compounds. Many essential oils are dense in exactly these compounds. Cats therefore accumulate metabolites that other animals clear easily.

Dogs metabolise most essentials oils adequately but are still vulnerable at high concentrations, particularly to pennyroyal, tea tree, and pine.

The ASPCA Animal Poison Control Center maintains an active list. The following appear consistently across veterinary toxicology literature as high-risk for cats:

• Tea tree (melaleuca)
• Pennyroyal
• Pine and wintergreen
• Sweet birch
• Citrus oils at high concentration (limonene)
• Ylang ylang
• Peppermint (concentrated)
• Cinnamon leaf and clove (eugenol)
• Lavender at high concentrations

Fragrance oils sold for IFRA category 12 (candles) are formulated to combust at the loads listed on the SDS. Most use synthetic aroma chemicals rather than steam-distilled botanicals, so they avoid the metabolic risk profile of essential oils. They are not zero-risk, but they are the safer choice when a cat or dog shares the room.

Always check the SDS. If a fragrance oil contains a high percentage of natural terpenes, treat it with the same caution as an essential oil.

Three things to do every time:

• Ventilate. An open window during burn is the single biggest mitigation.
• Never burn in a small room (under {{AREA:10}}) where the pet cannot leave.
• Reduce load. If you must use a sensitiser, drop fragrance load by 2 percentage points.