Nobody needs an air freshener. You pay for one and plug it in, and in the ones researchers have tested, most of what came out wasn’t named on the label. Here’s what researchers have found, and what to do instead.
Evidence key Strong Moderate Weak How we grade
You don’t know what’s in them
No law in the US, the EU or Australia requires air-freshener makers to list all their ingredients; a label can simply say 'fragrance'. Moderate evidence. Steinemann 2017
In two small product tests, the labels disclosed little of what researchers found in the air. In a German test of six air fresheners, more than 90% of the chemicals they released were not declared on the product. Moderate evidence. Steinemann 2017 In a test of 6 best-selling US air fresheners and laundry products, researchers found 98 chemical detections (58 different chemicals) released into the air; none appeared on any product label, and only 1 (ethanol) appeared on a safety data sheet. Moderate evidence. Steinemann 2009
4 of the 6 products released at least one chemical the Clean Air Act classifies as a hazardous air pollutant (acetaldehyde, chloromethane or 1,4-dioxane), and none was listed. Moderate evidence. Steinemann 2009
They’re built to put chemicals in the air
That’s the whole job. A plug-in scented-oil air freshener evaporated 1.5 g of product a day and kept its scent chemicals at 30-160 ug/m3 in the room over three days; its two largest emissions were fragrance esters (bornyl and benzyl acetate, 280-410 ug/m3), not the ozone-reactive terpenes usually studied. Moderate evidence. Singer 2006, Indoor Air
In lab tests, gel air fresheners released limonene at up to 1.5 mg per hour, far more than any other chemical measured. Moderate evidence. Jo 2008
In a car, you sit right next to it. Keeping a gel air freshener in a car raised the fragrance chemical limonene in the air the driver breathed 3.6-4.7 times, to about 19-28 ug/m3, during real commutes (10 cars tested). Moderate evidence. Jo 2008
With ozone around, some of them keep reacting
Scent chemicals in cleaners and air fresheners react with ozone that drifts in from outdoors to make formaldehyde: cleaning raised formaldehyde by 9-16 ppb for 4 hours, and a plug-in air freshener raised it by about 6 ppb for as long as it ran. Moderate evidence. Singer 2006
When scent chemicals from a pine-oil cleaner, an orange-oil degreaser and a plug-in air freshener met ozone in a lab chamber, about one formaldehyde molecule formed for every 3-5 ozone molecules they used up (yields of 20-30% in most tests). Strong evidence. Destaillats 2006
A car air freshener's own terpenes (alpha-pinene, beta-pinene, p-cymene, limonene) react with in-vehicle ozone to form ultrafine particles and irritant gases (formaldehyde, acetaldehyde, acrolein) that never appear on the product's ingredient list, because they are made in the cabin air, not sold in the bottle. Moderate evidence. Lamorena & Lee 2008 (J Hazard Mater)
We cover the chemistry in more detail in what scented cleaning does to your air.
Indoors, you breathe far more of it
A chemical released indoors is roughly 1,000 times more likely to be breathed in than the same amount released outdoors (exact when comparing the low end of each range; only ~100x at the high end, since the ranges overlap at 10⁻³), so cleaning products and air fresheners (about 1% of California's smog-forming emissions) may deliver an inhaled dose on the same scale as all outdoor sources combined. Strong evidence. Nazaroff & Weschler 2004
Who reports problems
About 1 in 6 adults (17%) in four countries said air fresheners or deodorizers make them unwell; of those, half reported breathing problems. Moderate evidence. Steinemann 2019
41% of US adults with asthma reported health problems from air fresheners, and 36.7% said they can't use a public restroom that has one. Moderate evidence. Steinemann 2018
About 1 in 4 Australian adults with asthma (24.0%) said a fragranced product had triggered an asthma attack; air fresheners were the most common trigger (14.1% of all asthmatics). Moderate evidence. Steinemann 2018
A Canadian birth cohort points the same direction for children, though it can’t single out one product. Scented spray products — spray and plug-in air fresheners, dusting sprays — were among the specific product types most strongly associated with childhood wheeze and asthma risk in this Canadian birth cohort. Moderate evidence. Parks et al. 2020
What to do instead
- Unplug it. Taking the air freshener out of the car removes its main added chemical: without one, in-car limonene was about 5-6 ug/m3. Moderate evidence. Jo 2008
- EPA's own first advice on indoor VOCs is to identify and remove the source, ventilate when products are used, and buy only what you will use soon, because even closed containers leak. Moderate evidence. US EPA 2026
- Air a room or clean it instead of scenting it: non-chemical alternatives such as opening windows and better hygiene are the first step in Klaschka's ten-step hierarchy for reducing fragrance exposure. Weak evidence. Klaschka 2020
- If a smell keeps coming back, find the source and fix it. Scent only covers it up.
- Switching cleaners too? EWG’s Guide to Healthy Cleaning rates household products, air fresheners included.
- At work, school or daycare, ask for air fresheners to go. Our workplace guide and school letter can help, and there’s a sign for that.
Every claim above shows its evidence grade and names its source, with a link wherever one exists. See all the indoor air facts and the claims we won’t make. Information, not medical advice.