Inhalation of essential oils and other plant essences is the fastest way to introduce the active compounds into the body.

Photo by Alexy Almond

Direct inhalation, which may be prescribed as part of clinical aromatherapy, can be done in a number of ways (e.g. placing a few drops of the oil in your palm and breathing with your palm in front of your nose, inhaling from a steaming bowl of water with a few drops of oil, etc.). Indirect inhalation is accomplished with the use of a room diffuser or the placement of a few drops of essential oil on a cotton ball near the person. Indirect inhalation will have a much slower introduction and likely a lower overall dose depending on duration of direct inhalation. Diffusers are a great option if you don’t want the intensity of direct inhalation.

This is a great summary of the medical science on aromatherapy from the National Cancer Institute:

PDQ® Integrative, Alternative, and Complementary Therapies Editorial Board. PDQ Aromatherapy With Essential Oils. Bethesda, MD: National Cancer Institute. Updated 10/25/2019. Available at: https://www.cancer.gov/about-cancer/treatment/cam/hp/aromatherapy-pdq.

We cover the evidence on the clinical use of aromatherapy elsewhere. For this article, the aromatherapy PDQ notes that inhalation of essential oils or application of diluted oils on the skin have a generally low toxicity profile.

What should I look for in a diffuser?

Performance

You want a diffuser that works excellently. Most essential oils will not be degraded for the purpose of a single aromatherapy session by a heat-based evaporative diffuser (they were already steam distilled in the first place). Many diffusers make the point that they diffuse oils, and function as a humidifier, and have mood lighting. This makes us wonder whether they have invested enough of the design and materials budget in diffusion performance.

Easy to Clean

Particularly with the water-based ultrasonic diffusers, you want a device that can be sterilized with a bleach or hydrogen peroxide solution easily every three days. The Mayo Clinic recommends that you drain the tank from a cool mist or ultrasonic humidifier daily and wipe down all of the interior surfaces. You also want to use distilled or demineralized water instead of tap to prevent mineral deposits that promote bacterial growth. There is no reason to turn what was supposed to be a health-promoting aromatherapy practice into the spread of allergens and infections.

Separately, you want to be able to clean any residue from a previous diffusion very easily.

Automatic Shut-off

You may be using the diffuser to help you meditate and then fall asleep. You want a device that will turn off automatically at relatively short intervals. As with any sensory exposure, our mind adapts to the constant presence of the smell of essential oils and will reduce our awareness of their presence. You become noseblind after a period, depending on the intensity of exposure and the chemical.

Durability

Things break. Most consumer products aren’t that well made to begin with. If you are paying a lot for performance, you should expect some degree of durability. If the diffuser is very low cost, it may not matter as much, except for the environmental impact, if it breaks down after not too long.

What Should We Get?

Given all of this, we don’t recommend that readers purchase ultrasonic diffusers with water mist or any other form of water-based diffusion. Odds are, you just aren’t going to clean it enough or use distilled or demineralized water. It is going to get all gross with intense bacterial films deep into the mechanism, and you are going to throw it away and potentially give up on diffusion. Lavender and Spice is reader-supported. As an Amazon Associate, we may earn commissions from qualifying purchases from Amazon.com. We are not compensated for any other links on this site.

1) Nebulizers

Aromatherapy nebulizers are different than the medical nebulizers intended to administer medicine through the mouth or nose, but they use the same underlying design. A stream of compressed air is passed by a reservoir tube with essential oils. The negative air pressure created by the stream of compressed air lifts essential oil particles into the stream, creating a fine mist that is released from the nebulizer chamber.

The nebulizers provides the purest delivery of indirect inhalation possible. They are fragile, which is primarily a concern during cleaning. The glass apparatus needs to be cleaned with rubbing alcohol to remove any deposits from oils that may clog the system.

Aromis Aromatherapy Nebulizer

The Aromis Nebulizer (Solum Nox Merus pictured here) is an all-glass nebulizer with wood base. The nebulizer runs ten minutes on and off with a four-hour auto-shut off feature. Somewhat unique in the class, there is an intensity adjuster knob.

The product gets good reviews for function, but also for the responsive customer service and availability of spare glass parts.

Radiance Nebulizing Diffuser

The Radiance Nebulizer from Organic Aromas is a bit more expensive than the Aromis, with a similar design and aesthetic. There is an LED light, which we don’t prefer, but may be attractive to some. Organic Aromas states that their nebulizer is quieter than others, so if the low hum from the Aromis bothers you, this could be a good alternative. There is an auto shut-off after 1 hour, which is a good duration. Some reviewers complain about the short run time and want to be able to run these all day at a very low setting. If the goal is a lower level of steady diffusion, the fan-based evaporators make more sense. In contrast to the positive comments about customer service on the Aromis, there are complaints about non-responsive customer service from Organic Aromas in Amazon customer reviews.

Minidiva Aromatherapy Diffuser

The Mindiva uses a different approach to atomizing than the condensed air and negative air pressure method used in the Aromis and similar glass nebulizers. Reviewers note that this does not produce the smell intensity that you get from the other diffusers in the class. It has a built-in battery that will run for 8 hours per charge. This is a good option if you don’t want the exposed glass parts and want something easier to clean than some of the enclosed nebulizers.

2) Fan-based evaporator with filter pads

This is an affordable and low-maintenance option for safe diffusion. You won’t have the intensity of odor from the nebulizer and there will be noise from the fan. If you are looking to scent a room moderately for a long period of time, this is an excellent option. The disposable filter pad pretty much eliminates the need to clean anything.

AromaAllure Essential Oil Diffuser

This is a small, quiet fan-driven, waterless diffuser well-suited to smaller rooms and less intense diffusion. You place the oil on the microfiber pad (which can be used with a single oil for a couple of months and are about $1/pad to replace) and turn the fan on. There is no clean-up. The fan runs on batteries and can also be plugged into a USB port. The unit runs for 30 minutes before shutting off.

Weljoy Portable Diffuser

This is just the cutest little thing ever: 2”x2”x1”. It has three fan speeds and can run for up to 5 1/2 hours on a rechargeable battery or continuously with USB cord. This has replaceable pads that can be used for a period of months with a single oil. This is perfect for travel, car, or desk use.