by erin stewart -303

The Different Kinds of Aromatherapy Diffusers

My very first diffuser was a gift from a colleague who I used to create recipes and photos and blog content for. It’s a lovely little nebulizing diffuser that is still running now, years after it was given to me. I’ve since acquired several others and I’m often asked about the differences between them, so I thought I’d go over that a bit today. If you’ve ever been curious about how the different kinds of diffusers work, wondered which kind is best for any given situation, or thought, “How do I clean this thing?” this blog post is for you.


The most simple kind of diffuser is a passive diffuser. A passive diffuser is something that isn’t necessarily meant to diffuse essential oils, but does by nature. A tissue, a cotton ball, a piece of dry clay, a porous stone included in a gemstone bracelet…these are all things that were not necessarily created to diffuse essential oils, but if you place a drop of essential oil on them, they will diffuse the essential oil into the air as the molecules evaporate from their surfaces. A drop of Black Spruce essential oil placed on a facial tissue that I wave throughout a room as I walk through it will leave the whole space smelling like a beautiful Spruce forest. A couple of drops of Lemon essential oil placed into a tray of clay charms can leave a bathroom smelling fresh for a few hours.

Affordability: $


Ultrasonic diffusers are probably the most popular kind of diffuser available on the market right now. They use water and ultrasonic vibrations to disperse the molecules of the essential oil into the air via a fine mist. They are easy to find, affordable, and are available in a wide variety of aesthetics so you can choose one that will look nice with your home’s decor.

If you choose to use thick, resinous, or citrus oils in an ultrasonic diffuser, you will want to clean the diffuser with distilled white vinegar after each use. (This is a good idea anyway, no matter which kind of essential oils you are using.) You definitely don’t want to let the thicker oils sit in the reservoir overnight. It is recommended to avoid using carrier oils in ultrasonic diffusers.

Ultrasonic diffusers produce a mist that is effective, but not as potent as that produced by some of the other options. This allows them to be run for longer periods of time (though you should still follow safety recommendations) while using small amounts of essential oil. Many ultrasonic diffusers have built-in timers that will automatically shut off the diffuser after a certain amount of time or that will alternate on/off every few minutes.

You can clean an ultrasonic diffuser by filling up the well with warm water and white vinegar and letting it soak for a few hours. (Make sure your diffuser is unplugged whenever you are cleaning it.) Pour out the water/vinegar mix and use a cotton swab to wipe away any residue that remains; be gentle around the disk. Rinse with cool water and run the diffuser for a few minutes with water only.

Affordability: $ – $$


Nebulizing diffusers also produce a fine mist, but they do not use water like the ultrasonic diffusers do. This is a great explanation of how they work. Resinous oils and carrier oils should generally be avoided with this kind of diffuser. Thick oils will do best when blended with other oils. Because nebulizing diffusers do not use water, they go through essential oils very quickly and can therefore be more expensive to use. (6-12 drops could last you several hours in an ultrasonic diffuser, but would only last for 10-15 minutes in a nebulizing diffuser. That said, they aren’t meant to be used the same way.) This video explains how to clean your nebulizing diffuser.

Nebulizing diffusers are best suited, in my opinion, to very specific applications. I prefer to use them most often for acute situations or respiratory ailments because they really ‘pack a punch’ when it comes to administering the essential oils. (Their use is much more treatment-like.) They get the job done quickly and effectively in a couple of minutes and can then be shut off until the next application. Because they do not use water, they produce a much more potent mist that quickly delivers the essential oil constituents to the blood stream.

The units themselves are usually more expensive than ultrasonic diffusers, but since I find them much more effective for certain situations, I think they are worth the few extra dollars. I also really appreciate that this kind of diffuser usually does not have any plastic parts that come into contact with the essential oil. The diffuser in the foreground of the picture below is a nebulizing diffuser.

Affordability: $ – $$


Reed diffusers are made of a narrow-necked vase or jar that is filled with essential oil diluted in a lightweight carrier oil. Reeds are placed into the jar through the neck and the aroma of the essential oils gradually travels up the length of the reeds and is dispersed into the air. The reeds need to be flipped over occasionally, but this style of diffuser does work well for applications meant purely for enjoyment. I love incorporating them into the decor of a room – you can use any narrow-necked glass or glazed vase to make your own. I often see them in the restrooms at natural foods stores as an alternative to chemical air ‘fresheners.’ You can see a reed diffuser in the background of the image below.

Affordability: $-$


Candle diffusers are usually made out of ceramic, soapstone, heat-tolerant glass, or other natural stone. They usually have a chamber for a tealight candle in the bottom and a bowl that sits on top of that chamber. The essential oil is usually placed into a carrier oil or water in the top bowl and then a tealight is placed underneath the bowl to heat the oil/water, causing the essential oil to evaporate into the room.

There are also other diffusers that work by applying heat (via electricity) to the essential oils to cause them to evaporate into the atmosphere. These diffusers are not generally recommended by most professionals or enthusiasts.

Affordability: $ – $$


Many of the travel diffusers I have used/seen either plug straight into the outlet in the car or plug into the USB port in the car (or elsewhere). Most of them seem to operate via a fan. Essential oils are placed onto a pad in the center of the unit and then, when the unit is plugged into the car, a fan blows across the pad and distributes the essential oils. I have also come across car units that are essentially mini ultrasonic diffusers and use water with the essential oil.

While I love the idea of a diffuser convenient for traveling / use in the car, I have yet to find one that lasts very long or works properly and therefore don’t recommend them at this time. If you have found one that you think is of exceptional quality and that has lasted longer than a few months for you, please do let me know. I generally prefer a clay diffuser or a plain cotton ball for use in the car.

Affordability: $-$


USB diffusers are made to be plugged into your laptop or some other device so you can diffuse oils near you while you are working at your computer. They periodically send up a little squirt of essential oil mist, much like the scented fragrance units you see in public restrooms. I have not yet found a USB diffuser that works very well or for very long, so I don’t generally recommend them. There are other options that are much more effective.

Affordability: $ – $


Novelty diffusers can include such things as pens that have a cotton wick inside, much like an aromatherapy inhaler has, jewelry pieces that have cotton pads incorporated into their design, and other such things. Jewelry pieces should be made of stainless steel. An example can be seen in the photo below.

Affordability: $ – $


For most families who are wanting to invest in a diffuser, I would recommend an ultrasonic diffuser. It’s generally the most versatile type of diffuser and is the easiest kind to maintain. For practitioners or those who deal with a lot of respiratory or sinus ailments, I would go with an ultrasonic diffuser first and then I would suggest adding a nebulizing diffuser to your collection second. They both have their place in the work of a practitioner or serious enthusiast. I also recommend passive diffusing – it’s easy, doesn’t require any electricity, and is an accessible method of diffusing for anyone because it doesn’t cost anything


Let me know in the comments below.

Much love,

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Erin Stewart is an herbalist, NAHA certified aromatherapist, organic gardener and urban homesteader. She grows over 150 kinds of aromatic and medicinal plants for her own apothecary and distills essential oils and hydrosols in her PNW garden. Erin is the founder of Floranella and of AromaCulture’s herbalism + aromatherapy magazine.

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7 thoughts on “The Different Kinds of Aromatherapy Diffusers”

  1. Thank you for saving me TONS of research time, Erin! As an Aromatherapy student, I have been getting the which diffuser and why question more frequently these days. Having only ever used a small nebulizing diffuser, I have no experience with any other type, and very little info to pass along when questioned. I was actually planning a morning research session this week sometime. And now, thanks to you "distilling" the info down in one place, I have a very good quick reference guide. And more time to study. Thanks, Erin!

  2. I have a Petal diffuser (Doterra) and personal fan diffuser that is plugged into the computer. Someone also gave me a diffuser made by NOW. The Doterra diffuser works just fine, good for small rooms. The personal desk diffuser works ok, but even after changing the felt pad, the smell tends to be the same no matter which oil I use! I don’t recommend the NOW diffuser- the water is placed in the upper cone, and is easily knocked off its base, spilling water all over the place. It’s even hard to pull the top off without leaking some water.

  3. I have a diffuser from Organic Aromas. It appears to be a heat diffuser based on a similar picture on one the site present. No water needed. I love it but need to know why it is not recommended.

    1. Erin Stewart

      Organic Aromas sells nebulizing diffusers – no water or heat. =) I have one from them and love it.

  4. Great post. I have a small diffusre with USB cable that has a pad and a fan that I use in my office. It is great for a small room. If I ever feel a cold coming on, I turn it on with my favorite, Spike Lavender. Keep up the great work. How about a future post explaining base, middle and top notes of essential oils.

  5. Can I use a Pier 1 Reed Diffuser fragrance (the ones that come with the reed diffuser sticks), in an ultrasonic mist diffuser?

    1. Erin Stewart

      I wouldn’t. Ultrasonic diffusers are made to work with water and essential oils, whereas a synthetic fragrance may have something else as its base, even a fatty oil perhaps, that could possibly ruin the elements in the diffuser. There’s also the consideration that you would be contaminating your diffuser with synthetics and therefore wouldn’t want to use it for therapeutics after that.

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