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About Candles, Natural Home Scents
Do Essential Oils Survive the Flame? What You Need to Know
If you’ve ever wondered whether essential oils hold up to the heat of a candle flame, you’re not alone. It’s one of the most common questions when it comes to natural candles. I know some brands use essential oils in room sprays or diffusers but avoid using them in candles – possibly due to concerns about heat sensitivity. But I believe that’s a missed opportunity. With the right formulation, candles can be a wonderfully soothing way to enjoy essential oils, combining ambient light with therapeutic fragrance. Understanding how heat affects essential oils is key to getting the most out of your aromatherapy experience – and making smarter, healthier choices when buying candles.
Why Heat Matters for Essential Oils
Essential oils are highly concentrated plant extracts. They contain delicate compounds that give each oil its unique scent and therapeutic effect. When exposed to high heat, especially direct flame, some of these compounds can begin to degrade.
These compounds include:
- Terpenes – found in citrus oils (limonene) and lavender (linalool); responsible for uplifting and calming effects
- Esters – common in lavender and chamomile; known for relaxing and anti-inflammatory properties
- Ketones – found in rosemary and eucalyptus; help with focus and mental clarity
- Phenols – present in clove and thyme; offer antimicrobial properties but are sensitive to heat
- Aldehydes – found in lemongrass and citronella; refreshing but prone to oxidation
That’s important because the breakdown of these molecules can:
- Alter or weaken the scent profile
- Reduce the oil’s therapeutic benefits
- In some cases, produce byproducts that may irritate sensitive noses
The Candle Burning Process: Where the Heat Hits
When a candle burns, the wax near the wick melts and creates a small pool. This liquid wax feeds the flame by travelling up the wick, along with the essential oils it carries. The hottest part is the tip of the flame – reaching temperatures of up to 1,400°C – while the outer edge of the wax pool remains much cooler, typically around 60–80°C.
That difference matters. Oils exposed to the direct flame or the wick’s base are more likely to degrade quickly. Oils further out in the wax pool evaporate more slowly, releasing their scent in a gentler, more controlled way.
Which Oils Are Most Heat-Sensitive?
Not all oils react to heat in the same way. Some are more fragile than others, especially those with lighter molecular structures (often top notes in a blend). These oils typically contain more volatile compounds like terpenes and aldehydes, which are highly sensitive to heat. However, for example, heating (up to 180°C) of basil, cinnamon, clove, oregano, thyme and some other oils did not influence either their antioxidant activities or their chemical composition.
When overheated, these compounds may oxidise or degrade into simpler molecules. In clean and ideal combustion, many of these will ultimately convert into carbon dioxide (CO₂) and water vapour (H₂O), though this also means their therapeutic value is lost. However, in incomplete combustion or overheating, they can form small amounts of irritants such as acrolein or formaldehyde, which may trigger sensitivities in some people.
Here are a few examples:
| Oil | Heat Sensitivity | Key Compounds | How They Break Down | Notes |
|---|---|---|---|---|
| Citrus oils (Lemon, Orange, Bergamot) | High | Terpenes (Limonene) | Oxidises into carvone, epoxides; or breaks into CO₂ & H₂O | Scent fades quickly; may trigger irritation |
| Peppermint & Eucalyptus | Medium | Ketones (Menthone), Oxides | Can degrade into acrolein and other aldehydes | Still effective if kept in the wax pool |
| Lavender & Chamomile | Low to Medium | Esters (Linalyl acetate), Alcohols | May hydrolyse into linalool and acetic acid | Mild degradation, often tolerable |
| Patchouli & Vetiver | Low | Sesquiterpenes | Remain stable or break into neutral compounds | Good choices for longer burns |
Please note: While some breakdown is inevitable, it doesn’t always result in total loss of value. But with high heat, the therapeutic profile can shift, reducing intended effects like relaxation or focus.
How Good Candle Design Protects Essential Oils
High-quality aromatherapy candles are formulated to minimise essential oil degradation. Here’s how:
- Use of soy wax or coconut wax: These burn at lower temperatures than paraffin, helping preserve oil integrity.
- Proper wick size and placement: Prevents overheating and keeps the wax pool consistent.
- Balanced oil distribution: Ensures oils stay mainly in the wax pool, away from direct flame.
- Correct oil ratios: Prevents overload, which can lead to poor burn and wasted scent.
These design principles aren’t just theoretical – they’re exactly how we craft our candles at Snug Scent. Every candle is carefully hand-poured using responsibly sourced soy wax, thoughtfully chosen essential oil blends, and a precisely selected wick to ensure a clean, even burn. This balance allows our candles to deliver a gentle but effective scent throw, without overheating the oils or compromising their natural benefits.
Alternatives to High-Heat Methods
If you’re particularly sensitive to scent or want to preserve essential oils fully, you might also try:
- Electric oil diffusers – no flame, consistent temperature
- Wax warmers – use gentle heat to melt wax without burning
- Room sprays – deliver instant fragrance without heat
- Reed diffusers – passive diffusion, no flame
These options offer different ways to enjoy essential oils without the thermal breakdown that candles can sometimes cause.
Final Thoughts
Yes, essential oils can lose some of their benefits when overheated – but that doesn’t mean you can’t enjoy them in candles. The key is quality. A well-designed candle using natural wax, a balanced wick, and the right essential oil blend can offer both beautiful scent and genuine aromatherapy benefits without compromising safety or effectiveness.
Want to dive deeper into how aromatherapy candles actually work? Read our full guide here
