Are Natural or Synthetic Fragrances Toxic?

Fragrances in cosmetic and household products are commonly used for many reasons—masking an unpleasant smell in the product itself, replacing a bad smell with something less offensive, or introducing a scent that invokes a pleasant emotion or memory. Studies show that bubblegum aroma evokes favorable memories of childhood.¹ A fresh cotton scent in laundry products assures people that the items are clean.

Our ability to smell is an integral part of health, which begs the question: Are artificially introduced fragrances, whether natural or synthetic, good for our health and the environment? 

Human Benefits and Tolerance of Fragrances Differ

Fragrances show promise in medicine. Homeopathy and aromatherapy frequently use odorant molecules like flavonoids and terpenes to activate neuro-immune systems and improve homeostasis.

For instance, cancer patients undergoing chemotherapy reported that inhaling a standardized lavender oil (two drops placed on a sponge and fixed to the shoulder) improved sleep depth and ease in falling asleep, reduced the number of wakeups and percentage of time awake, and benefited total sleep quality.²

Contrary to this, some people cannot tolerate fragrances of any type, natural or synthetic. Increasingly, clinics that treat complex chronic illnesses and allergies request that patients not use perfumed or scented personal care products before coming to the office. Studies show that fragrances can lead to migraines; cough and shortness of breath; dermatitis; eye, nose, and throat irritation; diarrhea; nausea; immune system dysregulation; mood disorders; and irregular heartbeats.³

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More research is needed to confirm that the chemicals used to make fragrances may be contributing factors to breast and prostate cancers, reproductive disorders, and autism in children.⁴

How Well We Smell

Why is there such polarity in enjoying, tolerating, and benefitting from concentrated scents? The “science of smell” era is only relatively new. In his book, The Forgotten Sense: The New Science of Smell and the Extraordinary Power of the Nose, Jonas Olefson, Ph.D., flips the false belief that humans have a poor sense of smell.⁵

Old science compared brain size with olfactory regions, called bulbs, to establish smell superiority.  They believed our oversized human brains overshadowed our relatively small olfactory brains, meaning our ability to smell was inferior. However, size has little to do with it, as our ability to smell is based on the capacity of interconnected neurons in the olfactory bulbs.

Even more surprising, this scientific revelation didn’t occur until 2015, when a zoologist, Matthias Laska, presented his findings.⁶ He found that humans are vastly more sensitive to odors than many animals, including rats, spider monkeys, and vampire bats (whereas mice and men have similar sensitivities to smell).

Other than dogs, who are olfactory superstars, humans have an excellent sense of smell and can even go nose-to-nose with dogs in certain situations.

Fragrances, Volatile Organic Compounds, Health and the Environment

Not only are humans better at smelling than once believed, but we now know that the immune, inflammatory, pituitary axis, and olfactory systems are closely linked, which could lead to new treatments using the nose as the entry point.^3,4 However, daily use of fragrances, other chemicals, and environmental contaminants may also lead to endocrine disruptions that damage human health and the environment.^3,4

All-natural or synthetic fragrances—whether in perfumes, deodorants, cosmetics, aromatic cleaning sprays, or other household products—have one thing in common: they are designed to evaporate.

Highly concentrated scents from plant sources or chemical compounds release volatile organic compounds (VOCs) at varying levels with evaporation.⁷ The most common VOCs in personal care and household products are formaldehyde, benzene, toluene, xylene, limonene (a terpene), glycol ethers (like 2-butoxyethanol), phthalates (like dibutyl phthalate), and chlorinated compounds.

While synthetic fragrances contain more VOCs, a study of 24 certified organic or naturally derived essential oils showed that all contained at least one or more VOC.⁷ Natural and synthetic limonene (the citrus scent in cleaning products) is the most common VOC.

Fragrances are like genies in the bottle; you can’t put them back. Once emitted, highly concentrated fragrances can react to sunlight, ozone, and other compounds to form new secondary air pollutants. This is particularly true for terpenes in some “green” and natural fragrances. For instance, when terpenes mix with ozone, they can form harmful compounds like formaldehyde, which is considered a carcinogenic.⁷

The collective levels of VOCs add up to alarming levels of air pollution, so much so that scientists have classified fragrances in personal care and household products as emerging indoor air pollutants.⁸ The National Oceanic and Atmospheric Administration (NOAA) warns that VOCs from perfumes, scented products, and paints can rival car pollution.⁹

While fragrances may be attractive to some and repellant to others, as we learn more about the human olfactory system and its relationship to the body, it may be wise to find alternatives to scented personal care and household products.

Ridding Your Home of VOCs

There are ways to reduce exposure to VOCs:

1. Buy unscented, fragrance-free household and personal care products.
2. Be aware of aerosols like dry shampoo, spray deodorant, and sunscreen.
3. Reduce your use of citrus-scented cleaning products that contain limolene.
4. Look for phthalate-free products.
5. Search out water-based, toxin-free nail polish.
6. Make a whole food- and spice-based natural air freshener with a simmer pot. Fill a pot of water with apple or citrus peels and aromatic whole spices like cinnamon sticks, cardamom pods, whole cloves, star anise, and peppercorns. Let simmer to release nature’s best fragrances.

References

1. Petratou, E., Paradisi, N., Diamantis, O. and Stalikas, A. (2020) Psychological Implications of Nostalgic Scents of Childhood. Psychology, 11, 2066-2080. doi: 10.4236/psych.2020.1112129. https://www.scirp.org/pdf/psych_2020123014152950.pdf
2. Yildirim D, Harman Ozdogan M, Erdal S, et al. The efficacy of lavender oil on fatigue and sleep quality in patients with hematological malignancy receiving chemotherapy: a single-blind randomized controlled trial. Support Care Cancer. 2025;33(2):79. Published 2025 Jan 8. https://pubmed.ncbi.nlm.nih.gov/39775962/
3. Rádis-Baptista G. Do Synthetic Fragrances in Personal Care and Household Products Impact Indoor Air Quality and Pose Health Risks?. J Xenobiot. 2023;13(1):121-131. Published 2023 Mar 1. doi:10.3390/jox13010010 https://pubmed.ncbi.nlm.nih.gov/36976159/
4. Kazemi Z, Aboutaleb E, Shahsavani A, Kermani M, Kazemi Z. Evaluation of pollutants in perfumes, colognes and health effects on the consumer: a systematic review. J Environ Health Sci Eng. 2022;20(1):589-598. Published 2022 Feb 3. https://pmc.ncbi.nlm.nih.gov/articles/PMC9163252/
5. Olefson, Jonas. The Forgotten Sense: The New Science of Smell and the Extraordinary Power of the Nose (Harper Collins, 2025).
6. Laska, M. (2015). Busting a myth: humans are not generally less sensitive to odors than nonhuman mammals. Chemical Senses, 537. https://www.researchgate.net/publication/292592026_Busting_a_myth_humans_are_not_generally_less_sensitive_to_odors_than_nonhuman_mammals
7. Nematollahi, N., Weinberg, J. L., Flattery, J., Goodman, N., Kolev, S. D., & Steinemann, A. (2020). Volatile chemical emissions from essential oils with therapeutic claims. Air Quality, Atmosphere & Health, 14(3), 365–369. https://researchonline.jcu.edu.au/64707/
8. Susmita Mukherjee, et al. Harmful effect of personal care products on ecosystem and the possible alternative approach. Biocatalysis and Agricultural Biotechnology 57, 1878-8181 (2024). https://www.sciencedirect.com/science/article/abs/pii/S1878818124000483?via%3Dihub
9. McDonald, B. C., de Gouw, J. A., Gilman, J. B., Jathar, S. H., Akherati, A., Cappa, C. D., Jimenez, J. L., Lee-Taylor, J., Hayes, P. L., McKeen, S. A., Cui, Y. Y., Kim, S.-W., Gentner, D. R., Isaacman-VanWertz, G., Goldstein, A. H., Harley, R. A., Frost, G. J., Roberts, J. M., Ryerson, T. B., & Trainer, M. (2018). Volatile chemical products emerging as largest petrochemical source of urban organic emissions. Science, 359(6377), 760–764. https://www.science.org/doi/10.1126/science.aaq0524