Why Most Scented Candles Are Toxic
Paraffin wax, synthetic fragrance, and lead wicks — what's really in your candles
The Problem with Paraffin Wax
The majority of candles sold in stores are made from paraffin wax, which is a byproduct of petroleum refining. When burned, paraffin releases volatile organic compounds (VOCs) including toluene and benzene — both of which are recognized carcinogens. A 2009 study from South Carolina State University found that burning paraffin candles in an enclosed room produced measurable levels of these chemicals in the air.
Paraffin soot also contains many of the same compounds found in diesel exhaust. The black residue you see accumulating on jar candle rims and nearby walls is not just cosmetic — those fine particles can be inhaled deep into the lungs.
Synthetic Fragrances
Most scented candles use synthetic fragrance oils rather than pure essential oils because they are cheaper and produce a stronger scent throw. The issue is that the term “fragrance” on a label can represent a blend of dozens of undisclosed chemicals. Fragrance formulations are considered trade secrets, so manufacturers are not required to list individual components.
Many synthetic fragrances contain phthalates, which are used to make scents last longer. Phthalates are endocrine disruptors — they interfere with hormone function and have been linked to reproductive issues in multiple studies. When a fragranced candle burns, these compounds become airborne and are inhaled directly.
Other common synthetic fragrance components include aldehydes, synthetic musks, and various solvents, all of which contribute to indoor air pollution.
Wick Concerns
The United States banned lead-core wicks in 2003, but imported candles may still contain them. Lead wicks release lead particles into the air when burned, and there is no safe level of lead exposure. Even after the ban, some candles use zinc-core or tin-core wicks, which can also release trace metals when burned.
Cotton wicks and wood wicks are the safest options. When shopping for candles, look for labels that specify “cotton wick” or “lead-free wick.” If the wick has a metal core (you can check by peeling back the cotton to look), avoid it.
Soot and Particulate Matter
All candles produce some particulate matter when burned, but paraffin candles produce significantly more than beeswax or soy alternatives. Fine particulate matter (PM2.5) from candle soot penetrates deep into the respiratory system and can aggravate asthma, allergies, and other respiratory conditions.
Jar candles tend to produce more soot than pillar candles because the jar restricts airflow around the flame. Candles with wicks that are too large for the candle diameter also produce excess soot, as do candles burned in drafty locations where the flame flickers constantly.
Indoor Air Quality Impact
Research measuring indoor air quality before and after candle burning consistently shows elevated levels of particulate matter, VOCs, and formaldehyde. In homes where candles are burned regularly — especially in smaller rooms with limited ventilation — these pollutants can accumulate to levels that exceed outdoor air quality standards.
The compounding effect matters. A single candle burned occasionally in a well-ventilated room poses minimal risk. But multiple scented paraffin candles burned daily in a closed bedroom or bathroom create meaningful, sustained exposure to airborne chemicals.
What You Can Do
- Switch to beeswax or soy candles with cotton wicks and essential oil fragrance. See our Beeswax vs Soy comparison guide for details.
- If you burn any candle, ventilate the room by cracking a window.
- Trim the wick to 1/4 inch before each burn to reduce soot.
- Avoid candles in small, enclosed spaces like bathrooms without ventilation fans.
- Consider flameless alternatives like essential oil diffusers or beeswax warmers for daily fragrance.