Some of what people breathe and rub on their skin every day has never been properly tested: whole perfumes, what scent turns into in the air, what happens once a bottle is opened. That isn’t a reason to relax. It’s the point. Here’s what the science doesn’t know yet, and who hasn’t asked.
Evidence key Strong Moderate Weak How we grade
What does breathing fragrance do over a lifetime?
In 1994 the industry left breathing out of its standard safety package, judging it not a concern. The industry's standard safety package for a fragrance ingredient in 1994 covered acute poisoning and skin effects (irritation, allergy, sun reactions); breathing it in was not tested, because the industry judged inhalation 'not a route of toxicological concern'. Moderate evidence. Ford 1994 (RIFM) Industry-funded
In animal and lab studies, common scent chemicals such as linalool, limonene and eugenol act on brain signaling systems; what lifelong low-level exposure does in healthy people has never been studied. Weak evidence. Pinkas 2017
Does anyone test the whole perfume, or just its ingredients?
A finished perfume is usually not toxicity-tested as a whole; its safety is assessed on paper from its secret ingredient list. When researchers tested 42 whole perfumes directly, they found hazards that ingredient-by-ingredient assessment is not designed to catch. Moderate evidence. Morlock & Heil 2025
Some ingredients never make it onto a safety sheet at all. Lab tests commissioned by US campaigners found 38 chemicals not listed on the label across 17 popular perfumes; 10 of them had no published safety data at all. Moderate evidence. Sarantis et al. 2010 (Not So Sexy), via Gilton 2011
What about the chemicals scent makes in the air?
Once in the air, scent chemicals such as linalool, ionones and the woody musk OTNE ('Iso E Super') reacted with ozone to form dozens of new oxidized chemicals, including a hydroperoxide. None of these was in the product. Moderate evidence. Wu 2024
Those new chemicals were never in the bottle, and the study didn’t test them for harm.
Does anyone test the version that’s actually in your bottle?
Scent chemicals change once a bottle is open. One key safety test only looked at the fresh version. The regulatory endocrine dossier on linalool tested 99.7%-pure, freshly handled material — not the air-oxidized linalool that forms in an opened bottle and that accounts for almost all of linalool's known allergy risk. Nobody has tested whether oxidized linalool is hormonally active. Moderate evidence. Hareng 2024 Industry-funded
For at least one ingredient, the published safety file was thin to begin with. For this fragrance ingredient there was no data at all on absorption, repeat-dose toxicity, developmental effects, genetic damage or cancer – the whole safety file is skin testing, and 8 of its 11 studies are unpublished company reports that outsiders cannot check. Strong evidence. Lalko 2007 (RIFM) Industry-funded
Are children more vulnerable?
Indoor irritant limits are built on studies of healthy young adults; a 2024 toxicology review found only one controlled irritation study in children (none under age 5) and concluded no evidence-based safety factor for children could be set. Strong evidence. Kleinbeck & Wolkoff 2024 Industry-funded More than 70% of the chemicals measured in childcare air had no health-based safety limit; several fragrance compounds were among 12 the authors flagged for further study. Moderate evidence. Hoang 2016
Are essential oils safe for kids?
As of 2019, the evidence that lavender or tea tree oil causes breast growth in young children consisted only of case reports: 11 children described in detail in 4 papers, with no controlled study. Moderate evidence. Hawkins 2020 Industry-funded The only population study of lavender and tea tree oils and hormone problems in children (556 US children) was too small to rule out a risk: regularly exposed children had 2.8 times the rate of endocrine diagnoses, with a 95% confidence interval from 0.35 to 22 times. Weak evidence. Hawkins 2021 Industry-funded Nothing in the industry's endocrine testing program covers tea tree oil, whose main constituent, terpinen-4-ol, was never tested. Strong evidence. Hareng 2024 Industry-funded
More in our guide for parents.
Do fragrance-free policies make people healthier?
We think they’re worth it, and in a US survey most people wanted them. But we haven’t found a solid study that measured the health effect of one, so we won’t claim they’re proven to work. That’s a study we’d love to see.
Researching any of this?
If you’re working on one of these questions, we’d like to hear from you and share your work with our readers. Email admin@ihateperfume.com.
Every claim above shows its evidence grade and names its source, with a link wherever one exists. See also the claims we won’t make. Information, not medical advice.