Sind Duftkerzen schädlich? Was die Messwerte zeigen

Are scented candles harmful? What the measurements show

Chigozie Ogbuebele

Are scented candles harmful? They are not completely harmless, but the reasons for this are usually different from those you read about in guides.

We pour our candles ourselves in Vienna and have worked our way through the body of research for this article. Some of it has corrected some of 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

Scented candles release particulate matter, nitrogen oxides, and VOCs when burned, significantly more than unscented candles. This was measured in a laboratory study published in the specialist journal Environment International in 2021. However, the calculated values for a normal living space were clearly below the applicable guidelines for most substances. Whether a risk arises depends on three things: how much you burn, how large and well-ventilated the room is, and how sensitive you are.

Based on this data, scented candles are not toxic in the sense of acute poisoning. It is about the exposure to indoor air over time.

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

What plays almost no role: what wax the candle is made of. That was the biggest surprise for us, and further down explains where this finding comes from.

If you belong to a risk group (asthma, allergies, pregnancy, infants in the household), caution is advisable. The consumer protection agency generally advises against scented candles. This is a precautionary recommendation and not evidence of acute damage from normal use, but it is part of it.

What is produced when burning

A candle is a small open combustion in your living room. Something inevitably arises.

Ultrafine particles. A single burning candle releases around 53 trillion ultrafine particles per hour, i.e., particles under 100 nanometers. The figure comes from the Leibniz Institute for Tropospheric Research in Leipzig. A team around Alfred Wiedensohler measured the particulate matter in 40 apartments in Berlin and Leipzig for over 18 months. The results were published in the specialist journal Indoor Air.

Particulate matter, measurable in everyday life. How much this affects the room is shown by a practical test by the measuring device manufacturer air-Q: Five scented tea lights in a room of about 22 square meters caused the particulate matter levels to rise from 6 to 7 to 26 to 28 micrograms per cubic meter over around two hours, i.e., about four times. The provider sells air measuring devices, so the result is therefore associated with an interest. Nevertheless, it serves as a rough estimate.

Soot when blowing out. If you blow out a candle, significantly larger, visible soot particles are produced, similar to those in tobacco smoke. The most inconspicuous action of the evening is one of the dirtiest.

More as soon as there is a draft. A flickering flame burns incompletely. With a wide open window, this creates significantly more smoke and pollutants than a steady flame. Ventilating is correct, just not while the candle is burning.

And how dangerous is that now? The 2021 study calculated its measured values for a normal living space and compared them with the applicable guidelines. For most substances, the values were significantly below. For three not always: nitrogen dioxide, acrolein, and benzo[a]pyrene.

However, this is not so clear, because the guidelines themselves are not. The authors point out that such values vary widely depending on their origin. For acrolein, the limit value is set so strictly that it is below the level of measurability. So you cannot determine whether it is being met.

What remains: In normal use in a ventilated room, the data do not speak for an acute risk. They are not enough for a clean bill of health.

Why the wax hardly makes a difference

The well-known narrative goes like this: Paraffin is a byproduct of petroleum processing, plant waxes like soy, rapeseed, and coconut are the better choice. We wrote it that way ourselves for a long time.

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

An assessment belongs to this: The study was funded by the candle associations of Europe, North America, and Latin America, as well as by seven fragrance manufacturers. The authors state that they have no conflicts of interest. Even so, an industry-funded study deserves a second look, especially with reassuring results. For the wax finding, it plays little role, because the industry sells all four types of wax. And the second main finding even goes against the interests of the funders: that it is precisely the fragrance that drives the emissions.

With soot, there are gradations: The consumer protection agency calls stearin partially better than paraffin. But "partially better with soot" is something completely different from "harmless because it is plant-based". And it is no reason to buy a candle.

What actually drives the emissions is the combustion itself: wick length, draft, flickering, extinguishing method, room size, burning duration. These are all things that you control when burning, not the manufacturer when pouring.

Our scented candles (classic, small, and in the tin) consist of rapeseed-coconut wax, our fragrance wax, and decorative candles like the Bubble candle made of soy wax or a soy wax blend. You will not find "paraffin-free" on the label anywhere. Based on this data, it would not be a quality feature.

What really matters: the fragrance

This is the real difference between a candle and a scented candle. And this is also the point that the authorities care about.

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

The mechanism is simple: The fragrance molecules are drawn into the wick with the liquid wax, get into the flame, and decompose there. What you smell is not just evaporated fragrance oil. A part of it burns. A study by the Fraunhofer Institute accordingly came to the conclusion that scented candles load the room air more heavily with polycyclic aromatic hydrocarbons (PAHs) and particulate matter than unscented wax lights. Salthammer's measurements additionally indicate that floral scents emit slightly more than spicy ones.

Allergens are the main topic of the authorities. The Federal Institute for Risk Assessment, briefly BfR, assesses the health risks of products on behalf of the federal government and recommends limit values. In 2013, it clearly positioned itself on candles: allergenic fragrances should only be allowed in them if they meet the requirements for cosmetics or toys. The reasoning is remarkably sober: fragrances fulfill no technological function in a candle. The BfR recommended limiting the over 55 allergenic fragrances that are already banned in toys. In the same document, it calls for completely banning lead from candles and proposes an upper limit of 0.6 nanograms per gram of candle for nickel.

The labeling problem. Only 26 potential allergens must be declared. Everything else can stand as "Parfum" in the data sheet. This is exactly where the well-informed buyer fails: You cannot read up on what you are breathing in.

And "essential" is no free pass. Cinnamaldehyde, the main fragrance substance of cinnamon oil, must be declared in cosmetics because of its allergy potential. Those interested in the fragrance families will find more about this in our article on fragrance notes.

Flameless is not automatically better. A study by Purdue University (Patra et al., Environmental Science & Technology Letters, 2025) investigated 15 commercially available fragrance wax melts. The released terpenes react with ozone in the room air to form nanoparticles, and in concentrations that are comparable to burning candles. An unscented melt produced none. The fragrance is the trigger, not the flame. This also applies to our fragrance wax, if you considered it the safer alternative because of the lack of flame.

Which scented candles are safe?

Which scented candles are safe? Strictly speaking, none, because every open flame emits. Further, the question brings you to what you recognize a candle that is acceptable with reasonable use.

Information about the fragrance. Can the manufacturer say which fragrances are in it and which allergens must be declared? This is the criterion that comes closest to the BfR finding, and that, in which small manufacturers have a real advantage because they know their supply chain.
A moderate fragrance concentration. More fragrance oil means more VOC. A candle that already jumps at you from two meters without being lit is no quality signal.
A wick without a metal core. Cotton, no wire.
The RAL quality mark, if present. It sets requirements for wax, wick, colors, and lacquer for lower-emission burning. The test is usually too complicated for small manufacturers. Its absence is therefore no warning signal, but its presence is a good sign.
Size suitable for the room. A candle in the bedroom is something different than five tea lights on 22 square meters.

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

Seven rules for burning

This is the part that actually makes a difference in everyday life. More about this in the guide Lighting candles correctly.

Trim the wick to a maximum of one centimeter, before every lighting. A wick that is too long means a flickering, incomplete combustion and thus formaldehyde, PAHs, nitrogen oxides, and soot. The right tool is in the Candle Care Set.
Do not blow out, but suffocate. Press the wick briefly into the liquid wax or use an extinguishing hat. Blowing out produces the coarse, visible soot particles.
Avoid drafts. Not in front of the open window, not in the passageway, not next to the fan.
Ventilate after extinguishing, not during. Combustion residues can be quickly removed from the room by ventilating.
Limit the burning duration. Two to four hours at a time are enough for the fragrance and keep the exposure manageable.
One candle instead of five. The quantity makes the dose. This applies to particulate matter just as much as to fragrances.
Do not let it burn in the bedroom while you sleep. That is not allowed anyway for fire safety reasons, and you do not want the exposure over eight hours either.

What counts and what does not

Influence factors on the pollutant load from scented candles
Factor	Influence	Who controls this
Wick length and draft	high	you
Extinguishing method	high	you
Number of candles and room size	high	you
Ventilating after burning	high	you
Fragrances and fragrance concentration	medium to high	Manufacturer
Wick with or without metal core	medium	Manufacturer
Type of wax (paraffin, soy, rapeseed, stearin)	low	Manufacturer

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

What we can say about our candles and what we cannot

We pour in Vienna, in small batches, by hand. What we can tell you about this:

Scented candles (classic, small, and in the tin): rapeseed-coconut wax. Fragrance wax and decorative candles consist 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 allergens that must be declared are in a specific fragrance, write to us, we will look it up. Exactly this information the BfR considers useful. And it is the point where a small manufacturer stands better than a large provider: We oversee our supply chain.
Wicks without metal core. For six of our classic scented candles, you choose between wooden wick and cotton wick, all others have a cotton wick. No wire, no lead, no nickel in the wick. This is one of the three topics where the BfR demands concrete limits.
A moderate fragrance concentration. We dose so that the fragrance carries the room, without taking it over.
Around 40 hours burning duration for our classic scented candle. At two and a half hours per evening, that is about 15 evenings.

What we do not claim: that our candles have no 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 would rather tell you here than after the purchase.

If you still want it cozy and follow the seven rules above: Our scented candles you find here, the candles with quote are our classic for gifting.

Three, with which you cannot go wrong after this article:

Golden Hour: tobacco, honey, and tonka. Warm and a bit more mature than most scented candles. You choose here between wooden and cotton wick, both without metal core. 24 euros, around 40 hours.
Parisian Butter: butter, milk, and vanilla, i.e., a croissant shortly after the oven. A gourmand fragrance from our Bakery Collection. 24 euros.
Sicilian Sunrise in the tin: lime, basil, mandarin. For 10 euros the easiest way to find out if you like a scented candle in the room at all, before you decide on a large one.

All three are deliberately not floral: Salthammer's measurements show slightly higher VOC values for floral fragrances than for spicy ones. The difference is not quantified and no reason for concern. But if you have the choice, you can also make it in this direction.

Conclusion

Scented candles are not harmless. They release particulate matter, VOCs, and nitrogen oxides, and scented candles more than unscented. The lever that most people think of, namely the right wax, is however the weakest of all. The strong levers are the trimmed wick, the steady flame, the suffocating instead of blowing out, one candle instead of five, and the window afterwards.

If you are sensitive, pregnant, or have a baby in the house, restraint is the right decision. For everyone else: consciously burn instead of casually and choose a manufacturer that can tell you what is in it.

Frequently Asked Questions

Which scented candles are safe for health?

No scented candle is completely safe, because every open flame releases particulate matter and VOCs. It becomes acceptable with moderate fragrance concentration, a wick without a metal core, a manufacturer that can provide information about the fragrances contained, and above all with proper burning: trim the wick to one centimeter, avoid drafts, suffocate instead of blowing out, ventilate afterwards.

Are scented candles toxic?

Not in the sense of acute poisoning. During burning, particulate matter, VOCs, and nitrogen oxides are produced, but in the laboratory study of 2021, the values calculated for a normal living space were clearly below the guidelines for most substances. It is about the exposure to indoor air over time. And that depends above all on how many candles you burn for how long and in which room.

Are scented candles carcinogenic?

Burning releases substances that are considered carcinogenic at high concentrations, including formaldehyde and polycyclic aromatic hydrocarbons. The concentration is what matters, not their presence: In the 2021 laboratory study, the calculated indoor air concentrations of most substances were well below the guideline values, although benzo[a]pyrene was detectable in five out of 24 measurement series. The German Federal Institute for Risk Assessment (BfR), which assesses health risks from products, also pointed out nickel, which is considered carcinogenic when inhaled, and proposed an upper limit of 0.6 nanograms per gram of candle.

Is home fragrance harmful in the bedroom?

Two things come together in the bedroom: a usually smaller room and a long period of stay. A candle should never be left unattended or burn overnight. This is ruled out for fire safety reasons alone. If you want to make the room smell nice, burn the candle one to two hours beforehand, extinguish it, and ventilate before you go to sleep.

Which home fragrance is not harmful to health?

There is no emission-free option. Even flameless alternatives are not automatically better: A 2025 study by Purdue University found nanoparticles in concentrations comparable to those from burning candles when melting scented wax, caused by the reaction of the fragrances with ozone in the indoor air. Simply ventilating creates the least exposure; if you want it to smell nice, the same applies to all options: use sparingly, ventilate well, and be more restrained in small rooms.

Are scented candles harmful during pregnancy?

There are hardly any robust studies specifically on scented candles during pregnancy. Because pregnant women belong to the groups for which authorities generally advise caution regarding indoor exposures, restraint is the obvious decision: Unscented candles or simply ventilating are the lower-risk choices. If in doubt, bring it up at your next prenatal check-up.

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

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