Fragrance Guide

Detailed information about how fragrances affect your health — plus a rating system you can use to keep it all organized.

Fragrance Ratings

I use these rating scales to stay consistent and unbiased as I rank scented products in the Interior Medicine shop from healthiest to least healthy. You can also use it as a guide when choosing candles, room fresheners, and other home scents, on your own. Scroll down to see all the information behind these scales.

Scent Types

Substrates

Throw Methods

Why three separate rating scales for fragrance?

Having three scales captures a more complete picture of a fragrance’s impact on your health by considering three things: what the scent itself is made from, what it is blended with (substrate), and how it is dispersed into the air in your home (throw method). For example, a perfectly healthy, 100% organic essential oil may be blended with a petroleum-based wax and burned, releasing a slew of unhealthy chemicals and smoke particles. On the other hand, a less-than-perfectly-healthy essential oil may be safely diffused in pure water, making it a healthier choice overall.

Fragrance Information

Click on bolded statements for links to more information and research.

What are 3rd party certifications? Why do they matter so much?

Third-party certification means that an independent group that didn’t make the product, has reviewed, tested, and verified the claims that the company making the product has made.

Third party certifications protect you. Just like greenwashing makes products appear better for the Earth than they really are, some companies intentionally make their products seem healthier for people than they really are, too.

Third Party Certifications

What is IFRA certification? Why is it rated so low?

The International Fragrance Association (IFRA) created its own Research Institute for Fragrance Materials (RIFM). This sounds good, but it’s entirely self-regulating. Its operations are opaque— they decide what chemicals are “safe” for use in fragrance (rather than requiring disclosure of ingredients, so consumers can make their own informed choice about whether its healthy enough for them or not.)

Many of the IFRA-approved ingredients, like benzophenone, methyleugenol and styrene, are known carcinogens.

When a company claims its scents are safe because they are IFRA-approved, it’s just not true. However, because they do limit some of the most harmful chemicals, I still consider IFRA-certified fragrance slightly better than uncertified fragrance.

Why are non-organic essential oils less healthy than organic ones?

Non-organic essential oils come from non-organic plants, which are typically grown with pesticides and synthetic fertilizers. These remain in the final product, in some cases, numbering in the dozens.

Scent

Are natural fragrances non toxic?

No. Natural fragrance, aroma, parfum, luxury scenting, and fragrance oil are all innocent-sounding words for the same thing: they’re synthetic fragrances. Synthetic fragrances are made in a lab by blending various chemical scents.

The word “natural” isn’t defined or regulated in personal care products and fragrance in the United States, so the phrase “natural fragrance” can be legally used, and make the product seem healthier than it is.

Unless a fragrance’s ingredients are “100% essential oil,” it is not truly natural.

How do I know if a fragrance is synthetic?

Unless it is labeled “100% essential oil,” it is probably synthetic.

Are synthetic fragrances toxic?

Yes, synthetic fragrances are notoriously bad for your health. They contain phthalates, aldehydes, parabens and aluminum-based salts, and are linked with reproductive harm, asthma, heart disease, neurotoxicity, and more. There are 3,600+ synthetic fragrance chemicals currently in existence, and dozens can be combined into one scent.

What does substrate mean?

The definition of a substrate is, “an underlying surface or layer.” For home fragrance, this is whatever the scent is mixed with or attached to, or what the scent travels along for release into the room. For example, candle wax, candle wicks, incense sticks (which are usually bamboo coated in adhesive), water, resin, or plant materials like palo santo sticks, sage leafs, or pinecones.

Substrate

What is an example of a scent that would be in plain water?

Reed diffusers, electric evaporative diffusers, and regular spray bottles (non-pressurized) are all examples of delivery methods that rely on mixing a scent with water for release it into the room.

What are plant-based substrates?

Examples of substrates that are100% plant-based include: hemp or cotton candle wicks,100% coconut or soy candle wax, or sticks, or leaves.

This differentiates from substrates that are not plant-based, like regular candle wax, which is made of paraffin (which comes from petroleum), or the glues used to adhere scent to incense sticks.

What is a tallow candle?

Tallow is rendered animal fat, typically from beef or sheep. It’s similar to lard, and is what candles were made with until modern chemistry allowed us to create paraffin.

What is paraffin?

Paraffin is a petroleum-based wax. Most standard candles are made with paraffin. It’s extracted from petroleum as a part of the oil refining process, mixed with solvents, distilled, and then further processed — making it softer or harder, or adding dyes to make it colorful. Burning petroleum, solvents, chemical additives, and dyes pollutes your indoor air and is associated with many health problems.

Some candles are labeled “coconut wax blend” or “soy wax blend.” When you see the word “blend,” it is likely blended with paraffin.

Why are incense sticks toxic?

Standard incense is listed as the least healthy option here. That’s because incense, despite its association with spirituality and health, is surprisingly toxic when it burns. So much so that research groups have spent time and effort quantifying exactly what chemicals, and in what amount, are released upon burning incense sticks.

Most incense sticks are proprietary, meaning they won’t disclose what the exact ingredients are. Typically, they are made of a combination of the following: 21% (by weight) of herbal and wood powder, 35% of fragrance material, 11% of adhesive powder, and 33% of bamboo stick.

When they burn, they release 4 times the amount of Particulate Matter as a cigarette, several poisonous gases (carbon monoxide, nitrogen dioxide, and sulfur dioxide), polylcyclic aromatic hydrocarbons (PAH’s), formaldehyde, and phthalates. Wow! If you must burn incense, I recommend using ones that have 100% ingredient disclosure— and use sparingly in a well-ventilated room.

What is evaporation or manual diffusion?

For the purposes of this guide, evaporation and manual diffusion are the two ways in which scent moves into the air with the least manipulation, and the least change in its properties.

Liquid scent is naturally drawn into the air by evaporation over time, much like a puddle evaporates on a sunny day. This same process happens with reed diffusers, or after using a regular spray bottle (not pressurized aerosol) to spritz a scent into the air.

Electronic evaporative diffusers promote the same process, just faster. Think of using a small fan to encourage the scent to evaporate into the air.

Throw Method

What is nebulized or ultrasonic diffusion?

These are common diffuser types that potentially change the molecular size of the scent. Some claim to make scents “nanoparticles,” and while I can’t verify that’s truly what happens, I view them with some caution. Nanochemicals are so small, they can cross through our cell walls and even through our blood-brain barrier. The technology as a whole is very new, so while this may turn out to be a safe delivery method for scent, I still think regular evaporative diffusers are healthier options until we know more.

What are aerosols?

Think about spray paint, or a Febreze air freshener spray, when you think about what aerosols are. An aerosol is technically a suspension of particles in air, and requires a fancy can with a compressed gas to propel it out of the can into a very fine mist.

Room fresheners typically come in compressed gas aerosol cans. Plug-in air fresheners are miniature versions— these use a tiny electrical circuit instead of your finger to “press the button” and release scented aerosol.

(FYI, regular spray bottles are not aerosols.)

What are propellants?

Propellants are compressed gasses in aerosol cans that force the scent out in its powerful, misty form. In the “olden days,” this gas was CFCs, or chlorofluorocarbons. However, CFC’s were banned because they were contributing to a big hole in the ozone layer. Now, other gasses are used instead. These are released along with the scent, so it’s important to use safe ones.

What is the difference between nitrogen and other gas propellants?

Harmful gasses are still used as the propellant in aerosol scent sprays. Benzene, a well-known human carcinogen, of which there is no level of safe exposure to, was found in many personal care aerosol sprays in 2021, forcing a major recall of those items. Ethanol may be a propellant that contains trace amounts of benzene (a carcinogen).

Some home fragrance aerosols use acetone and propane as propellants.

Nitrogen gas is currently considered the safest gas propellant. It is generally considered non-toxic and safe as part of an aerosol can.

So, avoid aerosols as scent delivery systems whenever you can. If you read the Safety Data Sheet and it specifically shows Nitrogen is the propellant, it is less dangerous than other options.

Why are candles bad for you?

Combustion — AKA, burning anything, including beeswax candles, paraffin candles, incense, even palo santo and sage — exposes you to smoke which is filled with fine particulate matter (PM 2.5), carbon monoxide, nitrogen dioxide, sulfur dioxide. Depending on whether or not the scent you’re burning is organic or synthetic, it also releases other gasses, VOCs, and phthalates into the air.

PM 2.5 is related to heart and lung disease, cancer, and is increasingly associated with developing dementia. It is the primary reason wildfire smoke and outdoor air quality warnings are issued, and is best kept to a minimum inside your house.

If you do decide to burn scents indoors, ensure they’re 100% organic and plant based, ventilate well, and I recommend use for special occasions only.

How can I make my candle less toxic?

The easiest way to do this is to use a candle warmer instead of burning the wick. Melting the wax gently lets the scent into your room without releasing the PM 2.5 particles that come from combustion.

(And of course, choosing candles made with organic essential oils and pure waxes in the first place will help, too. See the ones I recommend here.)

Fragrance Rating Guide