Are Candles Bad for You? Here Is What the Research Actually Says

TL;DR

• Burning a candle produces fine particles. The EPA says plainly that candles "can be sources of particulate matter."
• Lead-cored wicks were the serious hazard, and the CPSC banned them in 2003. If your candle was made in the US after that, this fear is dated.
• Soot output varies enormously between candles. The EPA cites research finding one candle type can produce 100 times more soot than another.
• Scented candles are the main driver of the black marks people find on walls and ceilings.
• The reassuring studies and the concerning ones both exist, and this post reports both rather than picking the flattering half.
• Trim your wick, cut drafts, and ventilate. Those three habits do most of the work.

Are candles bad for you?

Candles are not the health emergency the internet sometimes claims, but they are also not nothing, because burning anything indoors puts particles into the air you breathe. That is the honest starting point. A candle is a small controlled fire in your living room, and combustion has byproducts. How much it matters depends on the candle, the room, the ventilation, and how many you burn at once. The research below is specific about all four. I sell flameless wax melts, so I have an obvious interest here, which is exactly why every claim on this page links to the source it came from.

What does the EPA say about candles?

The EPA's own review states that burning candles can release particulate matter, and that lead-cored wicks could push indoor lead above recommended thresholds. That review is EPA/600/R-01/001, published in January 2001 by the Office of Research and Development. Its abstract opens with the sentence most articles skip: "Burning candles and incense can be sources of particulate matter." The lead half of that finding no longer applies to candles sold in the US, for reasons covered in the next section. The particle half still does. Read the date carefully. This is a literature review from 2001, and the candle market changed after it.

Are candles with lead wicks still sold?

No. The CPSC banned lead-cored wicks in 2003, so candles legally sold in the United States have not contained them for over twenty years. The Consumer Product Safety Commission "voted unanimously to ban the manufacture and sale of lead-cored wicks and candles with lead-cored wicks," after determining they "could present a lead poisoning hazard to young children." The ban covers imported candles too. This is the single most-repeated candle scare online and it describes a product that was outlawed in 2003. If you read a warning about lead wicks that does not mention the ban, that article is recycling a source older than the fix.

Does burning candles create soot?

Yes, and the amount varies wildly between candles, which is why two people can have completely different experiences with the same habit. The EPA review cites research finding that "one type of candle can produce as much as 100 times more soot than another type." Measured elemental carbon emission rates ran from under 40 to 3,370 micrograms per gram of candle burned. That is not a small spread. It means "are candles sooty" has no single answer. A well-made candle with a properly sized wick, burned without a draft, produces very little. A cheap over-wicked candle in a hallway with a ceiling fan produces a lot.

The EPA's own conclusion is that "sooting can be reduced by keeping candle wicks short, drafts to a minimum, and burning unscented candles." That last item is inconvenient for most of the candle industry, and it is in the document.

Are scented candles worse than unscented?

For soot, yes. The EPA review states directly that "scented candles are the major source of candle soot deposition." A restoration industry paper on soot damage reaches the same conclusion from the cleanup side, calling scented candles "the major culprits in the candle soot deposition phenomenon." Fragrance oils change how the wax burns. This is a fair place to note that my product is scented too. Wax melts are warmed rather than burned, so the soot mechanism does not apply, but the fragrance question does, and I cover that honestly further down.

What causes black soot on walls?

Black marks on walls and ceilings are called black soot deposition, and scented candles are the leading indoor cause, though not the only one. The EPA notes that this problem "is also referred to as ghosting, carbon tracking, carbon tracing, and dirty house syndrome," and that complaints "have risen significantly since 1992." The restoration paper explains why the marks form in patterns rather than evenly. Experiments by US Steel in the early 1970s found patterned deposition began when a surface was just 3.3 degrees Fahrenheit cooler than its surroundings. Past an 8 degree difference, "severe discoloration occurred." That is why soot traces your wall studs and ceiling joists.

Why does candle soot spread through the whole house?

Candle soot particles measure roughly .03 to 3 microns, so they stay airborne long enough to travel well beyond the room the candle is in. The restoration paper adds a modern wrinkle: tighter, better-sealed homes exchange less air with outside, so what goes into the air stays there longer. It also reports that "in some instances, noticeable soot damage can develop within a few hours of lighting the candles." Worth saying clearly: this is a trade paper by a certified restorer, not a peer-reviewed study, and it is roughly twenty-five years old. Cite it for how ghosting works, which is what restorers deal with daily, and not as a medical finding.

Is the black mark on my wall definitely from candles?

No, and blaming the candle first is a common mistake. The same restoration paper lists several non-candle causes of ghosting: fiberglass attic insulation, vehicle exhaust from an attached garage, ordinary dust, soil filtration through the building envelope, and fume fading. Before you throw out your candles, look at where the marks are. Staining above a garage door, along an exterior wall, or in a room with no candle history points somewhere else. A cold-spot pattern on a ceiling can come from insulation gaps regardless of what you burn. Diagnose it before you treat it.

Are candles bad for your lungs?

No study I found measured lung outcomes from ordinary home candle use, so anyone giving you a confident answer is going past the evidence. What has been measured is particles in the air. A 2025 study in Scientific Reports tracked particulate matter around a burning scented candle and compared it against a blank sample. At the candle, PM10 peaked at 1.52 times baseline five minutes in, then fell to 0.83 by sixty minutes. Three meters away, PM2.5 peaked at 1.62 and PM1 at 1.98, both at thirty minutes.

Those are modest multiples of a room's normal baseline, not a scare number, and the pattern the authors describe is that finer particles travel further and linger longer than coarse ones. Report those figures with the distance and the time attached or the claim stops being true.

Are scented candles toxic?

The peer-reviewed answer says no for normal use, and the study that says so deserves a label. Petry and colleagues, publishing in Regulatory Toxicology and Pharmacology in 2014, concluded that "under normal conditions of use scented candles do not pose known health risks to the consumer." That conclusion rests on chamber measurements fed into two exposure models, one of which is the RIFM 2-box indoor air dispersion model. RIFM is the Research Institute for Fragrance Materials, the fragrance industry's own research institute. That does not make the finding wrong. It does mean you should know whose model produced the exposure estimate before you treat it as the last word.

So what does the research actually conclude?

Both things at once, which is why articles that quote only one half of the EPA review mislead you. The EPA document reports that the European Candle Association and a separate 1994 analysis found no health hazard even in a deliberately extreme scenario of thirty candles burning four hours in a 50 cubic meter room. The same conclusions section reports that burning several candles "exceeded the EPA's 10-6 increased risk for cancer for acetaldehyde and formaldehyde, and exceeded the RfC for acrolein." The EPA then adds its own caveat: those guidelines "are not designed specifically for indoor air quality issues, so these conclusions are subject to interpretation." Reassurance and concern, in the same document, from the same agency.

What do lung health experts recommend?

The American Lung Association takes the strictest position of any source here, and it does not spare scented products of any kind. Its fragrance guidance advises readers to "choose fragrance-free products whenever possible" and to "avoid air fresheners, scented candles, and incense." It recommends removing odor sources "through regular cleaning instead of masking odors with fragrances," and opening windows and doors for ventilation whenever you do use scented products. I am quoting that accurately rather than trimming it, because that advice covers my wax melts too. If fragrance-free is right for your household, that is a legitimate answer and I would rather you know it.

How do you burn a candle more safely?

Trim the wick to a quarter inch before every burn, keep the candle out of moving air, and stop the burn at four hours. The National Candle Association recommends trimming to 1/4 inch and clearing debris from the wax pool, because leftover trimmings "will add more fuel to the candle than it's designed to handle." It advises against fans, air conditioning, open windows, and foot traffic, since "moving air can disturb the flame, resulting in those pesky black marks on the glass." It also recommends stopping at four hours, because carbon builds on the wick and mushrooms into "a dangerously large flame." Add ventilation and you have covered most of what the research supports.

Frequently Asked Questions

Are candles bad for you?

Burning candles releases particulate matter, which the EPA states directly. How much depends on the candle, the draft, and the room. A trimmed wick in still air with some ventilation puts you at the low end of a range that spans a hundredfold difference between candle types.

Do candles still contain lead?

Not in the United States. The CPSC banned lead-cored wicks and candles containing them in 2003, and the ban applies to imported candles as well.

Are scented candles worse than unscented ones?

For soot, yes. The EPA review states that "scented candles are the major source of candle soot deposition," and its conclusions recommend burning unscented candles as one way to reduce sooting.

What causes black marks on walls above a candle?

Black soot deposition, also called ghosting. Soot particles between .03 and 3 microns settle on surfaces that are slightly cooler than their surroundings. A restoration industry paper cites experiments showing patterning starts at a 3.3 degree Fahrenheit difference and turns severe past 8 degrees.

Is candle smoke bad to breathe?

Measured particle levels near a burning candle run at modest multiples of baseline rather than dangerous concentrations, per a 2025 Scientific Reports study. No study I located measured lung outcomes from ordinary home use, so the honest answer is that ventilation is sensible and alarm is not supported.

Should I stop using candles?

That depends on your household. The American Lung Association recommends avoiding scented candles and choosing fragrance-free products where possible, advice that also covers scented wax melts. If you keep burning candles, trim the wick, avoid drafts, and ventilate.

Sources cited

One last thing, since you asked about flames

I make flameless wax melts, so the reason I know this research is that I had to decide whether my own product was honest. Warming wax skips combustion, which removes soot, smoke, and the ghosting on your walls, and it removes the open flame. It does not remove fragrance from your air, and the American Lung Association guidance above applies to my melts as much as to anyone's candle. If you want scent with less of what the EPA measured, scoopable soy melts let you warm a small portion at a time in a ventilated room, and you can ask me exactly what is in them.

About the Author

Natile Barnes is the Founder and Maker at Custom Crafts and Scents. She hand-pours small-batch soy wax melts and meets customers face to face at the Northpoint Mall popup in Alpharetta, GA, where she happily answers questions about ingredients, fragrance, and safe use.

About Custom Crafts and Scents

Custom Crafts and Scents is a flameless home fragrance brand based in Alpharetta, GA. We make handmade, small-batch soy wax melts, plate and wax warmers, reed diffusers, room and wall sprays, and car refreshers, all without open flames or plugs. Find us online at customcraftsandscents.com or in person at our Northpoint Mall popup.