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 in advice columns.

We hand-pour our candles in Vienna, and we've worked our way through the current research for this article. Some of it has led us to correct our own product texts. Here is what was actually measured, what matters in everyday life, and what you can watch out for when burning them.

The short answer

When burning, scented candles release fine dust, 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 resulting values calculated 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 causing acute poisoning. It is about the load on the indoor air over time.

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 – orange peel just as much as fresh wall paint. Some are harmless, others irritate the airways.

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

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

What is produced when burning

A candle is a small open combustion in your living room. Something is inevitably produced as a result.

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

Fine dust, measurable in everyday life. A practical test by the measuring device manufacturer air-Q shows how strongly 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 about two hours – about four times as much. The provider sells air measuring devices, so the result is linked to a vested interest. Even so, 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 when there is a draft. A flickering flame burns incompletely. With a window wide open, significantly more smoke and pollutants are formed than with a steady flame. Ventilating is correct – just not while the candle is burning.

So how dangerous is this? The 2021 study extrapolated its measurements to a normal living space and compared them to current guidelines. For most substances, the values were well below these. For three of them, this was not always the case: nitrogen dioxide, acrolein, and benzo[a]pyrene.

However, it is not that clear-cut, because the guidelines themselves are not. The authors point out that such values vary widely depending on their origin. For acrolein, the limit is set so strictly that it is below the level of detectability – so you cannot even determine if it is being met.

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

Why the wax barely matters

The familiar narrative goes like this: Paraffin is a byproduct of petroleum processing, 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 this was published 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. 24 measurement series in total. The result, in their own words: No single wax type showed a consistently better emission profile than the others.

Some context is required: The study was funded by the candle associations of Europe, North America, and Latin America, as well as by seven fragrance manufacturers. The authors declare no conflicts of interest. With an industry-funded study, a second look is always worthwhile, especially regarding reassuring results. For the wax finding, it matters little, because the industry sells all four types of wax – and the second main finding actually goes against the interests of the sponsors: that it is the scent, in particular, that drives emissions.

When it comes to soot, there are variations – the consumer protection agency cites stearin as being slightly better than paraffin in some cases. But "slightly better in terms of soot" is something entirely different from "harmless because it's plant-based." And it is not a reason to buy a candle.

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

Our scented glass candles consist of rapeseed-coconut wax, our other candles of soy wax or a soy wax blend. You won't find "paraffin-free" on our labels – based on this data, it would not be a quality feature.

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 authorities are concerned about.

The scent is the driver, not the wax. The same 2021 study found a range of 70 to 14,388 micrograms of VOCs per candle per hour – a difference of more than two hundredfold, and it is almost entirely due to the scent. For formaldehyde, the range was from 17 to 360 micrograms per candle per 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, enter 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 consequently concluded that scented candles load the indoor air more heavily with polycyclic aromatic hydrocarbons (PAHs) and fine dust than unscented wax candles. Salthammer's measurements additionally indicate that floral scents emit slightly more than spicy ones.

Allergens are the main topic for the authorities. The German Federal Institute for Risk Assessment (BfR) evaluates the health risks of products on behalf of the federal government and recommends limit 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 calls for lead to be completely banned from candles and proposes an upper limit of 0.6 nanograms of nickel per gram of candle.

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 inhaling.

And "essential" is not a free pass. Cinnamaldehyde, the main fragrance component of cinnamon oil, must be declared in cosmetics due to its allergy potential. Anyone interested in fragrance families can find more on this 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 room air to form nanoparticles – in concentrations comparable to burning candles. An unscented melt created none. The scent is the trigger, not the flame. This also applies to our scented wax – in case you thought it was the safer version because of the lack of a flame.

Which scented candles are safe?

Which scented candles are safe? Strictly speaking, none, because every open flame emits. The more helpful question is how to identify a candle that is acceptable when used sensibly.

Transparency about the scent. Can the manufacturer say which fragrances are inside and which allergens must be declared? This is the criterion that comes closest to the BfR's findings – and it's the area where small manufacturers have a real advantage because they know their supply chain.
A moderate scent concentration. More fragrance oil means more VOCs. A candle that jumps out at you from two meters away while unlit is not a sign of quality.
A wick without a metal core. Cotton, no wire.
The RAL quality mark, if present. It sets requirements for wax, wick, colors, and varnish for lower-emission burning. Testing is usually too complex for small manufacturers – its absence is therefore not a warning sign, but its presence is a good sign.
Size appropriate for the room. A candle in the bedroom is something different than five tea lights in 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 – as beautiful as these claims may look on a label.

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 every lighting. A wick that is too long means a flickering, incomplete combustion – and thus formaldehyde, PAHs, nitrogen oxides, and soot.
Don't blow it out, suffocate it. Briefly dip the wick into the liquid wax or use a candle snuffer. Blowing it out creates the coarse, visible soot particles.
Avoid drafts. Not in front of an open window, not in a walkway, not next to a fan.
Ventilate after extinguishing, not during. Combustion residues can be quickly removed from the room by ventilating.
Limit burning time. Two to four hours at a time are sufficient for the scent and keep the exposure manageable.
One candle instead of five. The quantity makes the dose. This applies to fine dust just as much as to fragrances.
Do not leave it burning in the bedroom while you sleep – not for fire safety reasons anyway, and you don't want the exposure over eight hours either.

What counts and what doesn't

Influencing factors on pollutant exposure from scented candles
Factor	Influence	Who controls this
Wick length and drafts	high	you
Extinguishing method	high	you
Number of candles and room size	high	you
Ventilating after burning	high	you
Fragrances and scent 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 Vienna, in small batches. What we can tell you about this:

Scented glass candles: rapeseed-coconut wax. Our other 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 declarable allergens are in a specific scent, write to us – we will look it up. The BfR considers exactly this type of information to be useful. And it is the point where a small manufacturer stands in a better position than a large supplier: we oversee our supply chain.
Wicks without a metal core. For our scented glass candles, you can choose between a wooden and a cotton wick. No wire, no lead, no nickel in the wick – that is one of the three areas where the BfR specifically calls for limits.
A moderate scent concentration. We dose it so that the scent carries through the room without taking it over.
About 40 hours of burn time for our scented glass candle. With two and a half hours per evening, that's 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 is perhaps simply "no," and we would rather tell you that here than after the purchase.

If you still want it cozy and observe the seven rules above: you can find our scented candles here, the candles with sayings are our classic 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. You choose between a wooden and a cotton wick, both without a metal core. 24 euros, about 40 hours.
Parisian Butter – butter, milk, and vanilla, like a croissant fresh from the oven. A gourmand scent from our Bakery Collection. 24 euros.
Sicilian Sunrise in a tin – lime, basil, mandarin. For 10 euros, the easiest way to find out if you even like having a scented candle in the room before you decide on a large one.

All three are intentionally not floral: Salthammer's measurements show slightly higher VOC values for floral scents than for spicy ones. The difference is not quantified and is no cause for concern – but when you have a choice, you can choose in that direction.

Conclusion

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

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

Frequently Asked Questions

Which scented candles are safe for health?

No scented candle is completely harmless, as every open flame releases fine dust and VOCs. It becomes acceptable with a moderate concentration of fragrance, a wick without a metal core, a manufacturer that can provide information on the ingredients, and, above all, proper burning: trim the wick to one centimeter, avoid drafts, extinguish by snuffing rather than blowing out, and ventilate afterwards.

Are scented candles carcinogenic?

Burning them 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 a 2021 laboratory study, the calculated indoor air concentrations for most substances were well below the guidelines, 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 associated with products, also pointed to nickel—which is considered carcinogenic when inhaled—and proposed an upper limit of 0.6 nanograms per gram of candle.

Is room fragrance harmful in the bedroom?

Two factors come together in the bedroom: a usually smaller room and a long duration of stay. A candle should never be left burning there unattended or overnight—that is ruled out for fire safety reasons alone. If you want to scent 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 option. 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 the fragrances with ozone in the indoor air. Simple ventilation creates the least amount of pollution; if you want a scent, the same rule applies to all options: use sparingly, ventilate well, and be more reserved in small rooms.

Are scented candles harmful during pregnancy?

There are hardly any reliable studies specifically on scented candles during pregnancy. Because pregnant women belong to groups for which authorities generally advise caution regarding indoor pollution, restraint is the obvious choice—unscented candles or simply ventilating are the lower-risk options. If in doubt, bring this up at your next check-up.

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

For health-relevant emissions, hardly. 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 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.