Candles and Essential Oils: Healthy or harmful?

Fall is around the corner, and the cinnamon-scented pinecones are out in full force. I can’t stand that smell, but plenty of people love it. In fact, this is the time of year many people start burning pumpkin spice and similarly scented candles at home. But does this have any impact on health? And what about essential oils? I fully admit I LOVE the smell of lavender diffused throughout my office and house.

I’ve heard claims about health benefits and harms, so this week I dug into the research to answer a simple question: are there real health effects, good or bad, to burning candles or diffusing essential oils indoors?

Candle Components

All candles have two basic parts: wax and wick. The wax, which serves as the fuel, can be made from paraffin, soy, beeswax, coconut, palm, or blends of these. The wick is typically braided or twisted cotton that may have other fibers woven into it. When lit, the heat melts wax into liquid. The liquid is drawn up the wick, vaporizes, and ignites. The flame continues to melt more wax, creating a cycle. But what exactly gets vaporized into the air?

What's in the Air?

All candles, especially the scented ones, emit particulate matter (PM), volatile organic compounds (VOCs) and polycycle aromatic hydrocarbons (PAHs). An interesting study looked at candles made from palm, paraffin, soy, and stearin wax, each in floral, fresh, fruit, oriental, and spice scents, along with unscented versions, to see what they released into the air when burned. The researchers found that all candles gave off measurable substances, but the unscented candles consistently emitted the least.1

Another concern is phthalates. These are chemicals used in a variety of different goods including fragrances. Scented candles, specifically those containing synthetic fragrances, release phthalates into the air when burned.2 Phthalates are endocrine disrupting chemicals that can cause reproductive health problems, developmental delays, and endocrine and hormone disruption.3

Do these emissions reach meaningful levels outside of lab conditions? Do chronic exposures to smaller concentrations cause any long-term health issues? Some research says we don’t know due to limited studies and data. Others claim it’s fine, but those papers often have industry ties or conflicts of interest.4,5 What we do know: scented candles can trigger or worsen allergies and respiratory symptoms and good ventilation likely helps reduce these risks.6,7

Essential Oils and the Air

As a lover of diffused lavender oil, I hoped the data would prove diffusing essential oils superior to burning candles. There’s no combustion so you don’t get soot, PMs, PAHs or nitrogen oxide,  but there are still VOCs such as of terpenes and formaldehyde.8-11 Additionally, lavender and tea tree oils are endocrine disruptors.12

For most healthy adults, there is no strong evidence of toxicity from occasional or chronic exposure, but they can cause respiratory irritation, allergies, and headaches.13 Children, pets, and possibly pregnant women are a different story.14,15 Oils like camphor and eucalyptus contain monoterpenes which have demonstrated toxicity in children and small animals.16-18 The American Academy of Pediatrics has stated that the use of essential oils in infants, children, and adolescents should be avoided until more safety and efficacy data are available.19,20 Tea tree oils and several other essential oils have caused serious neurologic disorders in animals as well.21,22

What About the Health Benefits?

There are no reported health benefits to burning candles, but there are some with essential oils. Aroma therapy with essential oils has demonstrated stress reduction, mood enhancement, and relief of mild anxiety and sleep disturbances.23-27 There is even some evidence of improved brain activity, reduced blood pressure, and promoted relaxation. 25-27

Bottom Line

Candles and essential oils make your home smell great, but neither is completely without risk. Unscented candles emit fewer compounds than scented ones. Diffusing essential oils avoids soot and some combustion-related pollutants but still releases VOCs and can pose specific risks for kids, pets, and pregnant women. Some essential oils offer mild mental health benefits, but that doesn’t cancel out the need for caution.

If you love candles or essential oils, the decision is ultimately yours. Just make sure you have good ventilation and be especially careful around children and animals.

Disclaimer: Even though I’m a doctor, I’m not your doctor—and reading this blog does not establish a doctor–patient relationship. This information is intended for general educational purposes only and should not be taken as personalized medical advice. Always speak with your own healthcare provider before making decisions about your health.

References

  1. Salthammer T, Gu J, Wientzek S, Harrington R, Thomann S. Measurement and evaluation of gaseous and particulate emissions from burning scented and unscented candles. Environ Int. Oct 2021;155:106590. doi:10.1016/j.envint.2021.106590
  2. Ahn J-H, Kim K-H, Kim Y-H, Kim B-W. Characterization of hazardous and odorous volatiles emitted from scented candles before lighting and when lit. Journal of Hazardous Materials. 2015/04/09/ 2015;286:242-251. doi:https://doi.org/10.1016/j.jhazmat.2014.12.040
  3. Katsikantami I, Sifakis S, Tzatzarakis MN, et al. A global assessment of phthalates burden and related links to health effects. Environment International. 2016/12/01/ 2016;97:212-236. doi:https://doi.org/10.1016/j.envint.2016.09.013
  4. Petry T, Vitale D, Joachim FJ, et al. Human health risk evaluation of selected VOC, SVOC and particulate emissions from scented candles. Regul Toxicol Pharmacol. Jun 2014;69(1):55-70. doi:10.1016/j.yrtph.2014.02.010
  5. Heinze JE, Silverman A. Comment on “Characterization of hazardous and odorous volatiles emitted from scented candles before lighting and when lit”. Journal of Hazardous Materials. 2016/02/13/ 2016;303:171. doi:https://doi.org/10.1016/j.jhazmat.2015.07.011
  6. Al Khathlan N, Basuwaidan M, Al Yami S, Al-Saif F, Al-Fareed S, Ansari K. Extent of exposure to scented candles and prevalence of respiratory and non-respiratory symptoms amongst young university students. BMC Public Health. Jan 11 2023;23(1):80. doi:10.1186/s12889-023-15001-6
  7. Yun H, Seo JH, Kim YG, Yang J. Impact of scented candle use on indoor air quality and airborne microbiome. Sci Rep. Mar 25 2025;15(1):10181. doi:10.1038/s41598-025-95010-0
  8. Angulo Milhem S, Verriele M, Nicolas M, Thevenet F. Does the Ubiquitous Use of Essential Oil-Based Products Promote Indoor Air Quality? A Critical Literature Review. Environmental Science and Pollution Research International. 2020;27(13):14365-14411. doi:10.1007/s11356-020-08150-3
  9. Karr G, Quivet E, Ramel M, Nicolas M. Sprays and Diffusers as Indoor Air Fresheners: Exposure and Health Risk Assessment Based on Measurements Under Realistic Indoor Conditions. Indoor Air. 2022;32(1):e12923. doi:10.1111/ina.12923
  10. Kim PG, Lee A, Shin J, et al. Determination of Terpene Levels After the Use of Essential Oil Diffusers in Vehicles and Studio Apartments Using Passive Sampling. The Science of the Total Environment. 2023;879:163071. doi:10.1016/j.scitotenv.2023.163071
  11. Schwartz-Narbonne H, Du B, Siegel JA. Volatile Organic Compound and Particulate Matter Emissions From an Ultrasonic Essential Oil Diffuser. Indoor Air. 2021;31(6):1982-1992. doi:10.1111/ina.12845
  12. Sharma K, Lanzilotto A, Yakubu J, et al. Effect of Essential Oil Components on the Activity of Steroidogenic Cytochrome P450. Biomolecules. Feb 8 2024;14(2)doi:10.3390/biom14020203
  13. Wolkoff P, Nielsen GD. Effects by inhalation of abundant fragrances in indoor air – An overview. Environ Int. Apr 2017;101:96-107. doi:10.1016/j.envint.2017.01.013
  14. Yancu D, Sanderson T. Essential oils disrupt steroidogenesis in a feto-placental co-culture model. Reprod Toxicol. Dec 2019;90:33-43. doi:10.1016/j.reprotox.2019.08.010
  15. Dosoky NS, Setzer WN. Maternal Reproductive Toxicity of Some Essential Oils and Their Constituents. Int J Mol Sci. Feb 27 2021;22(5)doi:10.3390/ijms22052380
  16. Kolassa N. Menthol Differs From Other Terpenic Essential Oil Constituents. Regulatory Toxicology and Pharmacology : RTP. 2013;65(1):115-118. doi:10.1016/j.yrtph.2012.11.009
  17. Lanzerstorfer P, Sandner G, Pitsch J, et al. Acute, Reproductive, and Developmental Toxicity of Essential Oils Assessed With Alternative in Vitro and in Vivo Systems. Archives of Toxicology. 2021;95(2):673-691. doi:10.1007/s00204-020-02945-6
  18. Wojtunik-Kulesza KA. Toxicity of Selected Monoterpenes and Essential Oils Rich in These Compounds. Molecules (Basel, Switzerland). 2022;27(5):1716. doi:10.3390/molecules27051716
  19. McClafferty H, Vohra S, Bailey M, et al. Pediatric Integrative Medicine. Pediatrics. Sep 2017;140(3)doi:10.1542/peds.2017-1961
  20. Kemper KJ, Vohra S, Walls R. American Academy of Pediatrics. The use of complementary and alternative medicine in pediatrics. Pediatrics. Dec 2008;122(6):1374-86. doi:10.1542/peds.2008-2173
  21. Khan SA, McLean MK, Slater MR. Concentrated Tea Tree Oil Toxicosis in Dogs and Cats: 443 Cases (2002-2012). Journal of the American Veterinary Medical Association. 2014;244(1):95-99. doi:10.2460/javma.244.1.95
  22. Nicholson SS. Toxicity of Insecticides and Skin Care Products of Botanical Origin. Veterinary Dermatology. 1995;6(3):139-143. doi:10.1111/j.1365-3164.1995.tb00057.x
  23. Caballero-Gallardo K, Quintero-Rincón P, Olivero-Verbel J. Aromatherapy and Essential Oils: Holistic Strategies in Complementary and Alternative Medicine for Integral Wellbeing. Plants (Basel). Jan 29 2025;14(3)doi:10.3390/plants14030400
  24. Vora LK, Gholap AD, Hatvate NT, et al. Essential Oils for Clinical Aromatherapy: A Comprehensive Review. Journal of Ethnopharmacology. 2024;330:118180. doi:10.1016/j.jep.2024.118180
  25. Sattayakhom A, Wichit S, Koomhin P. The Effects of Essential Oils on the Nervous System: A Scoping Review. Molecules (Basel, Switzerland). 2023;28(9):3771. doi:10.3390/molecules28093771
  26. Choi NY, Wu YT, Park SA. Effects of Olfactory Stimulation With Aroma Oils on Psychophysiological Responses of Female Adults. International Journal of Environmental Research and Public Health. 2022;19(9):5196. doi:10.3390/ijerph19095196
  27. Schneider R, Singer N, Singer T. Medical Aromatherapy Revisited-Basic Mechanisms, Critique, and a New Development. Human Psychopharmacology. 2019;34(1):e2683. doi:10.1002/hup.2683

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