Sind Duftkerzen schädlich? Was die Messwerte zeigen

Are scented candles harmful? What the measurements show

Chigozie Ogbuebele

Are scented candles harmful? They aren’t entirely harmless—but the reasons for this are usually different from those you read about in advice guides.

We pour our own candles in Vienna, and for this article, we have worked our way through the current research. Some of it has led us to revise our own product descriptions. Here is what was actually measured, what matters in everyday life, and what you can pay attention to when burning them.

The short answer

When burning, scented candles release fine particulate matter, nitrogen oxides, and VOCs—significantly more than unscented candles. This was measured in a laboratory study published in the journal Environment International in 2021. However, the calculated levels for a standard living space were clearly below current safety guidelines for most substances. Whether a risk arises depends on three things: how much you burn, the size of the room and how well it is ventilated, and how sensitive you are.

According to this data, scented candles are not toxic in the sense of causing acute poisoning. The issue concerns the long-term exposure of indoor air.

By the way, VOC stands for volatile organic compounds. These are substances that transition into the air even at room temperature. Everything you can smell belongs to this category—from orange peel to fresh wall paint. Some are harmless; others irritate the respiratory tract.

What plays almost no role, however, is the type of wax the candle is made of. That was the biggest surprise for us, and you can read where this finding comes from further down.

If you belong to a high-risk group—asthma, allergies, pregnancy, or infants in the household—caution is advisable. The consumer protection agency (Verbraucherzentrale) generally advises against scented candles. This is a precautionary recommendation rather than evidence of acute harm during normal use, but it is worth noting.

What happens when you burn them

A candle is a small open combustion event in your living room. It inevitably produces emissions.

Ultrafine particles. A single burning candle releases about 53 trillion ultrafine particles per hour—particles under 100 nanometers in size. This figure comes from the Leibniz Institute for Tropospheric Research in Leipzig. For 18 months, a team led by Alfred Wiedensohler measured fine particulate matter in 40 apartments in Berlin and Leipzig. The results were published in the journal Indoor Air.

Fine particulate matter, measurable in everyday life. A practical test by measuring device manufacturer air-Q shows how much this impacts a room: five scented tea lights in a room of about 22 square meters caused fine dust levels to rise from 6–7 to 26–28 micrograms per cubic meter over roughly two hours—about a fourfold increase. As the provider sells air quality monitors, the result is linked to a commercial interest. Nevertheless, it serves as a useful benchmark.

Soot when extinguishing. When you blow out a candle, significantly larger, visible soot particles are created—similar to those in tobacco smoke. The most inconspicuous move of the evening is one of the dirtiest.

More, the more drafts there are. A flickering flame burns incompletely. With windows wide open, this creates considerably more smoke and pollutants than a steady flame. Ventilating is correct—just not while the candle is burning.

So, how dangerous is it? The 2021 study projected its measurements to a standard living space and compared them to current guidelines. For most substances, the values were well below these limits. For three, they were not always: nitrogen dioxide, acrolein, and benzo[a]pyrene.

However, it is not quite that clear-cut, as the guidelines themselves are not uniform. The authors point out that these values vary widely depending on their source. In the case of acrolein, the limit is set so strictly that it is below the threshold of measurability—so it is impossible to determine whether it is being met.

What remains: Under normal use in a ventilated room, the data does not suggest an acute risk. However, it is not enough to issue an all-clear.

Why the wax barely matters

The common narrative goes like this: paraffin is a petroleum byproduct, while plant-based waxes like soy, rapeseed, and coconut are the better choice. We ourselves wrote this for a long time.

The most thorough investigation on the subject appeared in 2021 in the journal Environment International. A team led by indoor air chemist Tunga Salthammer burned four types of wax under laboratory conditions—palm wax, paraffin, soy wax, and stearin—each with five different scent variants and once without scent. A total of 24 measurement series. The result in their own words: No single wax type showed a consistently better emission profile than the others.

Some context: The study was financed by the candle associations of Europe, North America, and Latin America, as well as seven fragrance manufacturers. The authors declare no conflicts of interest. Nevertheless, it is worth taking a second look at industry-funded studies, especially when the results are reassuring. The wax finding matters little, as the industry sells all four types of wax—and the second main finding even goes against the funders' interests: that it is the fragrance itself that drives emissions.

Regarding soot, there are nuances—the consumer protection agency mentions stearin as sometimes being better than paraffin. But "sometimes better regarding soot" is something entirely different from "harmless because it's plant-based." And it is no reason to buy a candle.

What actually drives emissions is the combustion process itself: wick length, drafts, flickering, extinguishing method, room size, and burn time. These are all things that you control when burning the candle—not the manufacturer when pouring it.

Our scented glass candles are made of rapeseed-coconut wax; our other candles are made of soy wax or a soy wax blend. You will not find "paraffin-free" on any of our labels—based on this data, it would not be a quality indicator.

What really matters: the scent

This is where the actual difference between a candle and a scented candle lies—and this is also the point that concerns regulatory authorities.

The fragrance is the driver, not the wax. The same 2021 study found a range for VOCs of 70 to 14,388 micrograms per candle per hour—a difference of more than two hundred times, and it is almost entirely attributable to the scent. For formaldehyde, the range was 17 to 360 micrograms per candle per hour. Unscented candles were consistently at the lower end.

The mechanism is simple: fragrance molecules are drawn into the wick with the liquid wax, get caught in the flame, and decompose there. What you smell is not just evaporated fragrance oil—a portion of it burns. A study by the Fraunhofer Institute correspondingly concluded that scented candles load indoor air with polycyclic aromatic hydrocarbons (PAHs) and fine dust more heavily than unscented wax candles. Salthammer’s measurements further indicate that floral scents emit slightly more than spicy ones.

Allergens are the main topic for authorities. The German Federal Institute for Risk Assessment (BfR) evaluates health risks of products on behalf of the German government and recommends threshold values. In 2013, it took a clear position on candles: allergenic fragrances should only be permitted in them if they meet the requirements for cosmetics or toys. The reasoning is remarkably sober: fragrances serve no technological function in a candle. The BfR recommended restricting the more than 55 allergenic fragrances that are already banned in toys. In the same document, it demands that lead be banned from candles entirely and proposes a maximum limit of 0.6 nanograms per gram of candle for nickel.

The labeling problem. Only 26 potential allergens must be declared. Everything else can be listed as "parfum" on the data sheet. This is exactly where the well-informed buyer hits a wall: you cannot read what you are breathing in.

And "essential" is not a free pass. Cinnamaldehyde, the primary fragrance component of cinnamon oil, must be declared in cosmetics due to its allergy potential. If you are interested in fragrance families, you can find more in our article on fragrance notes.

Flameless is not automatically better. A study from Purdue University (Patra et al., Environmental Science & Technology Letters, 2025) examined 15 commercially available scented wax melts. The released terpenes react with ozone in the indoor air to form nanoparticles—in concentrations comparable to burning candles. An unscented melt produced none. The fragrance is the trigger, not the flame. This also applies to our scented wax—in case you thought it was the safer option due to the lack of a flame.

Which scented candles are safe?

Which scented candles are safe? Strictly speaking, none, because every open flame emits. A more useful question is how to identify a candle that is acceptable under reasonable usage.

Transparency about the fragrance. Can the manufacturer say which fragrance substances are included and which allergens must be declared? This is the criterion that comes closest to the BfR findings—and it is where small workshops have a real advantage because they know their supply chain.
A moderate fragrance concentration. More fragrance oil means more VOCs. A candle that hits you from two meters away even when unlit is not a sign of quality.
A wick without a metal core. Cotton, no wire.
The RAL quality mark, if available. It sets requirements for wax, wick, colors, and varnish for lower-emission burning. Certification is usually too expensive for small workshops—so its absence is not a warning signal, but its presence is a good sign.
Size appropriate to the room. A candle in the bedroom is something different than five tea lights in a 22-square-meter room.

What is not a useful criterion: "paraffin-free," "100% natural," "vegan," or "soy wax" as a health promise. According to measurement data, the type of wax says practically nothing about the relevant emissions—no matter how nice these labels look on a package.

Seven rules for burning

This is the part that actually makes a difference in everyday life.

Trim the wick to a maximum of one centimeter before each lighting. A wick that is too long causes a flickering, incomplete burn—and thus formaldehyde, PAHs, nitrogen oxides, and soot.
Don't blow it out, smother it. Dip the wick briefly into the liquid wax or use a candle snuffer. Blowing them out creates coarse, visible soot particles.
Avoid drafts. Not in front of an open window, not in a hallway, not next to a fan.
Ventilate after extinguishing, not during. Combustion residues can be quickly removed from the room by ventilating.
Limit burn time. Two to four hours at a time is enough for the scent and keeps the load manageable.
One candle instead of five. The dose makes the poison. This applies to fine dust just as much as it does to fragrance substances.
Do not let it burn in the bedroom while you sleep—not for fire safety reasons, and you don't want the exposure over eight hours anyway.

What counts and what doesn't

Factors influencing pollutant load from scented candles
Factor	Influence	Who controls it
Wick length and drafts	high	you
Extinguishing method	high	you
Number of candles and room size	high	you
Ventilating after burning	high	you
Fragrance substances and concentration	medium to high	manufacturer
Wick with or without metal core	medium	manufacturer
Wax type (paraffin, soy, rapeseed, stearin)	low	manufacturer

Four of the five most effective levers are in your hands. That is the truly good news of this article.

What we can say about our candles—and what we can't

We pour by hand in small batches in Vienna. Here is what we can tell you about them:

Scented candles in glass: Rapeseed-coconut wax. Our other candles are made of soy wax or a soy wax blend.
We know our fragrance oils. They come from a manufacturer that provides safety data sheets. If you want to know which declarable allergens are in a specific scent, write to us—we will check. This is exactly the information the BfR considers useful. And it is the point where a small workshop stands better than a large provider: we have an overview of our supply chain.
Wicks without metal core. For our scented glass candles, you can choose between a wood or cotton wick. No wire, no lead, no nickel in the wick—this is one of the three areas where the BfR explicitly demands limits.
A moderate fragrance concentration. We dose them so that the scent carries through the room without overpowering it.
About 40 hours of burn time for our scented glass candle. With two and a half hours per evening, that is about 15 evenings.

What we do not claim: that our candles have zero emissions. That plant wax makes them healthy. That a scented candle is suitable for everyone. If you have asthma or are pregnant, the answer might simply be "no," and we prefer to tell you that here rather than after you've made a purchase.

If you still want it cozy and follow the seven rules above: you can find our scented candles here; the candles with sayings are our classics for gifting.

Three that you can't go wrong with after reading this article:

Golden Hour – Tobacco, honey, and tonka. Warm and a bit more mature than most scented candles. Here you choose between a wood and cotton wick, both without a metal core. 24 Euro, about 40 hours.
Parisian Butter – Butter, milk, and vanilla, like a croissant fresh out of the oven. A gourmand scent from our Bakery Collection. 24 Euro.
Sicilian Sunrise in a tin – Lime, basil, and mandarin. At 10 Euro, the easiest way to find out if you even like having a scented candle in the room before committing to a large one.

All three are intentionally not floral: Salthammer’s measurements show slightly higher VOC levels for floral scents than for spicy ones. The difference is not quantified and is no cause for concern—but if you have the choice, you might as well choose in that direction.

Conclusion

Scented candles are not harmless. They release fine dust, VOCs, and nitrogen oxides, and scented candles do so more than unscented ones. However, the lever most people think of—the right wax—is actually the weakest of all. The strong levers are the trimmed wick, the steady flame, smothering instead of blowing out, one candle instead of five, and opening the window afterward.

If you are sensitive, pregnant, or have a baby in the house, restraint is the right decision. For everyone else, the rule is: burn mindfully instead of on the side—and choose a manufacturer who can tell you what’s inside.

Frequently asked questions

Which scented candles are safe for your health?

No scented candle is completely harmless because every open flame releases fine dust and VOCs. It becomes acceptable with a moderate fragrance concentration, a wick without a metal core, a manufacturer who can provide information about the fragrance substances used, and—most importantly—correct burning: trim the wick to one centimeter, avoid drafts, smother instead of blowing out, and ventilate afterward.

Are scented candles carcinogenic?

The burning process produces substances that are considered carcinogenic in high concentrations, including formaldehyde and polycyclic aromatic hydrocarbons. The crucial factor is the concentration, not the presence: in the 2021 lab study, the calculated indoor air concentrations for most substances were well below the guidelines, though benzo[a]pyrene was detectable in five of 24 measurement series. The German Federal Institute for Risk Assessment (BfR), which evaluates health risks of products in Germany, also pointed to nickel, which is considered carcinogenic when inhaled, and proposed a maximum limit of 0.6 nanograms per gram of candle.

Is room fragrance in the bedroom harmful?

In the bedroom, two things come together: a usually smaller room and a long duration of stay. A candle should never burn there unattended or overnight—that is ruled out by fire safety regulations alone. If you want to fragrance the room, burn the candle for one to two hours beforehand, extinguish it, and ventilate before going to sleep.

Which room fragrance is not harmful to health?

There is no emission-free version. Even flameless alternatives are not automatically better: a 2025 study from Purdue University found nanoparticles in wax melts at concentrations comparable to burning candles—triggered by the reaction of fragrances with ozone in the indoor air. The least amount of pollution is produced simply by ventilating; if you want a scent, the same rule applies to all versions: use sparingly, ventilate well, and be more restrained in small rooms.

Are scented candles harmful during pregnancy?

There are hardly any reliable studies specifically on scented candles during pregnancy. Because pregnant women are among the groups for whom authorities generally advise caution regarding indoor air pollutants, restraint is the obvious choice—unscented candles or simply ventilating are the lower-risk options. In case of doubt, mention this at your next check-up.

Does it make a difference whether the candle is made of soy wax or paraffin?

Hardly, in terms of health-relevant emissions. A 2021 laboratory study in the journal Environment International compared palm wax, paraffin, soy wax, and stearin in 24 measurement series and found that no single type of wax had a consistently better emission profile than the others. There are minor differences regarding soot, but the type of wax is the weakest influencing factor. What actually counts is the fragrance content—and how you burn the candle.