It's a reasonable question. You burn a candle in your living room, you breathe the air in that room, and at some point you wonder whether that's actually fine.
The honest answer is: for most people, in normal conditions, well-made candles used sensibly are not a documented health risk. But there are real nuances worth understanding, and some claims in the home fragrance industry overstate things in both directions.
Here's what the evidence actually says.
What candles produce when they burn
All combustion — candles, cooking, fireplaces, your boiler — produces carbon dioxide and water as primary byproducts. Candles also produce small amounts of VOCs (volatile organic compounds) and particulate matter (soot), with the quantity depending on the wax, wick, and fragrance used.
This is not unique to candles. You produce more VOCs cooking a meal on a gas hob than burning a candle in the next room. The question isn't whether combustion produces byproducts — it always does. The question is whether those byproducts, at the levels generated by candle use in a typical home, are harmful.
For most people, in a reasonably ventilated space, the answer from available research is: not at a meaningful level.
The paraffin debate — what the evidence actually says
You've probably seen claims that paraffin candles release benzene, toluene, or other toxic chemicals. This gets repeated constantly in home fragrance marketing. The actual evidence behind it is much thinner than those claims suggest.
The most widely cited source is a 2009 study from South Carolina State University, which claimed paraffin candles release harmful compounds. That study was never published in a peer-reviewed journal, its methodology has been questioned by multiple independent researchers, and it has never been replicated. The US National Candle Association — not a neutral party, admittedly — commissioned independent testing that found no evidence of harmful VOC levels at typical use.
The legitimate concerns about paraffin are real but more modest: it is a petroleum derivative, and it does produce more soot than plant-based waxes. More soot means more particulate matter in the air. Over time and with frequent use in poorly ventilated spaces, that's worth factoring in — not because of acute toxicity, but because particulate matter in indoor air is an ongoing consideration.
Plant-based waxes (soy, coconut) burn more cleanly and produce less soot. That's a genuine advantage. But the gap between "burns a bit cleaner" and "paraffin is toxic" is considerable, and a lot of brands blur it on purpose.
Fragrance oils and essential oils — are they safe?
Both can be used safely in candles. The key is regulation and testing.
Fragrance oils (synthetic, or partly synthetic) used in reputable UK and EU candles are required to comply with IFRA standards — the International Fragrance Association's guidelines, which set maximum use levels for hundreds of fragrance compounds based on safety testing. Phthalate-free fragrance oils (which is what we use) have had the most commonly questioned compounds removed from the formula.
The assumption that "natural = safer" with essential oils doesn't always hold. Some pure essential oils are skin sensitisers, phototoxic, or — particularly for cats — genuinely toxic when concentrated. IFRA compliance matters more than whether the fragrance is synthetic or natural.
The honest position: IFRA-compliant, phthalate-free fragrance oils in candles and wax melts are safety-assessed and used at regulated levels. "Natural" fragrance isn't automatically safer and sometimes isn't regulated as carefully.
Wicks — what actually matters
Lead wicks were used in some candles decades ago and were linked to lead particulate release. They were banned in the UK and EU, and in the US by the Consumer Product Safety Commission in 2003. This is not a current concern with candles from reputable UK makers.
What does matter is wick size relative to candle diameter. An oversized wick creates a large flame, more soot, and incomplete combustion. A properly sized cotton wick, trimmed to around 5mm before each burn, burns more cleanly and produces noticeably less soot. This is one of the most practical things you can do for air quality.
Ventilation — the most underrated factor
More than the wax type, more than the fragrance, ventilation makes the biggest practical difference to air quality when burning candles.
Burning a candle in a sealed room for several hours concentrates whatever byproducts are produced. Opening a window — even slightly — changes the picture significantly. This doesn't mean you need a draughty room. It means not sealing every gap and burning candles in a bathroom with no ventilation for hours on end.
Practically: a slightly open window or door, candles burned for 2–3 hours at a time rather than all day, and extinguishing properly rather than blowing (which sends a plume of smoke into the room) covers most of the ventilation consideration.
Who should be more careful
For most healthy adults, moderate candle use in ventilated spaces is not a concern. There are groups where more care is warranted:
- People with asthma or respiratory conditions. Any combustion product can be a trigger. Plant-based waxes with cotton wicks produce less particulate matter, which helps, but the safest option for this group may be wax melts — which involve no combustion at all.
- Babies and young children. Developing lungs are more sensitive. Keep burning candles out of rooms where very young children sleep, and prioritise good ventilation.
- Cats. Cats metabolise many compounds differently to humans and dogs, and are particularly sensitive to some fragrance compounds. More on this in our separate guide on wax melts and pets — but concentrated fragrance near cats warrants care regardless of the product type.
- People with fragrance sensitivities. Some people react to fragrance compounds regardless of their safety classification. If you're sensitive, the solution is usually ventilation and shorter burn sessions rather than avoiding fragrance products entirely.
Practical steps for safer candle use
- Trim your wick to 5mm before each burn. Smaller flame, less soot, cleaner burn.
- Ventilate. A slightly open window makes a meaningful difference.
- Don't burn for more than 3–4 hours at a time. Let the room air out between sessions.
- Extinguish with a snuffer. Blowing out sends smoke into the room. A snuffer doesn't.
- Choose cotton wicks. Standard in reputable UK candles, but worth checking.
- Choose plant-based wax where possible. Less soot than paraffin — a real, if modest, improvement.
- Keep candles away from draughts. A flickering flame burns less cleanly and produces more soot.
Where wax melts fit in
Wax melts have a meaningfully different risk profile to candles because there's no combustion involved. The wax is heated, not burned. No flame means no soot, no combustion byproducts, no particulate matter from burning.
The fragrance oil safety consideration still applies — IFRA compliance and phthalate-free formulations matter just as much. But for people with respiratory conditions, or anyone who wants fragrance at home without any combustion, wax melts in an electric warmer are the cleaner option.
Our botanical wax melts use coconut wax and phthalate-free fragrance oils — and since there's no flame involved, the air quality picture is simpler.
Frequently Asked Questions
Is paraffin wax toxic?
The widely repeated claim is largely based on a 2009 study that was never peer-reviewed and has not been replicated. In a normally ventilated home, paraffin candles are not documented to be a health risk for most adults. Paraffin does produce more soot than plant-based waxes — that's a legitimate reason to prefer alternatives — but "more soot" and "toxic" are different things, and a lot of brands conflate them deliberately.
Are scented candles bad for you?
For most people, in ventilated spaces, no. The main considerations are soot levels (trimming wicks helps), fragrance safety (IFRA-compliant formulations are safety-assessed), and ventilation. The risks are real but modest for typical use — and often overstated in marketing for "natural" alternatives.
Are candles bad for asthma?
Any combustion product can trigger asthma or respiratory conditions. Plant-based wax with cotton wicks produces less particulate matter than paraffin. Good ventilation makes a significant difference. For people who are particularly sensitive, wax melts — no combustion, no soot — are a lower-risk option for home fragrance.
Are wax melts safer than candles?
For air quality specifically, yes. No flame means no combustion, no soot, no particulate matter from burning. Fragrance safety considerations still apply either way. For anyone with respiratory sensitivities, or who just wants to remove combustion from the equation, wax melts in an electric warmer are the cleaner choice.
What makes a candle safer?
Plant-based wax (less soot), cotton wick trimmed to 5mm (smaller, cleaner flame), IFRA-compliant phthalate-free fragrance, good ventilation, 3–4 hour burn sessions rather than all day, and extinguishing with a snuffer. None of these is complicated — they just need to become habit.
