Are Soy Candles Toxic? What the Research Says

Unscented soy candle in an amber glass jar with a black lid — Shown: Unscented, 9 oz amber jar, $20

The short answer

Soy wax is a plant-based wax made from soybean oil. But no candle is soot-free once it's lit. The National Candle Association says plainly, "There is no such thing as a soot-free wax," and that sooting is mostly down to wick length and a disturbed flame, not the type of wax. That's why we don't call our candles "non-toxic" or "clean burning": nothing defines those words, and every flame makes some soot.

What soy wax is

Soy wax is made by hydrogenating soybean oil, which turns the liquid oil into a soft, solid wax. Ours is natural soy wax from US-grown soybeans, with a cotton and paper wick. Scented candles also contain fragrance oil; our Unscented candle doesn't.

Does soy burn cleaner than paraffin?

Not according to the National Candle Association, which represents makers of every kind of wax. It says all candle waxes "have been shown to burn cleanly, safely and in the same manner," and that no wax is "best." The bigger differences come from how a candle is made and burned. Our soy vs. paraffin guide compares the two in more detail.

What a 2021 study measured

Researchers at Germany's Fraunhofer WKI burned 24 test candles in a sealed chamber: four waxes with five fragrances, plus unscented candles, and measured gases and particles including carbon monoxide, formaldehyde, benzene and fine particles. In most cases the calculated indoor concentrations were well below health guidance values; the authors discuss the exceptions (nitrogen dioxide, acrolein and benzo[a]pyrene). Scented and unscented candles gave off significantly different mixtures. The study was designed with candle makers and fragrance houses, so read it with that in mind.

How to burn any candle with less soot

Trim the wick to ¼ inch before every burn.
Keep the candle out of drafts, fans and vents, which make the flame flicker and smoke.
Burn for no more than four hours at a time, and air out a small room.
Stop when about ½ inch of wax is left.

If you're sensitive to scent

If fragrance bothers you, or someone at home has asthma or another breathing problem, choose an unscented candle or a flameless one, and ask your doctor what's right for you. Our Unscented candle has no added fragrance, from $12.

This is general information, not medical advice. Sources: National Candle Association, elements of a candle: wax; Salthammer et al., Measurement and evaluation of gaseous and particulate emissions from burning scented and unscented candles, Environment International 155 (2021) 106590.

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Are Soy Candles Toxic? What Soy Wax Is and What Any Flame Gives Off