Essential oils for a diffuser and how much of them to use
Most essential oils suit a diffuser as long as they are thin enough to disperse: citrus, herbs, florals, the lighter woods and resins. Thick ones clog the machine, fragrance oils belong in a burner, and the dose is a few drops, not a capful.
By the editors of Aromatherapy Diffuser GuideUpdated 21 September 20265 min read
In short
- Sweet orange, lemon, rosemary, eucalyptus, geranium, cedarwood and frankincense disperse well; thick resins, absolutes and carrier oils do not.
- A pure essential oil shows a Latin name, plant part and method on the back label; a fragrance oil says parfum or aroma oil.
- A water diffuser takes a few drops per fill, a waterless machine its own pod or a neat oil; keep every bottle off bare skin and away from cats and birds.
Which essential oils suit a diffuser
The oils that work best are the thin, volatile ones: they turn to vapour readily and leave little behind.
- Citrus: sweet orange, lemon, grapefruit, bergamot. Bright, quick to lift and quick to fade, so they suit mornings.
- Herbs and leaves: rosemary, peppermint, eucalyptus. Clean and green, the usual choice for a hallway, bathroom or desk.
- Florals: lavender, geranium, ylang-ylang. Softer and longer-lasting, the evening end of the shelf.
- Lighter woods and resins: cedarwood, cypress, juniper, frankincense. They sit under a blend and keep it going after the citrus has gone.
The oils that do not belong in the machine
Some bottles are sold as essential oils and still make a poor fill: thick oils clog a nebuliser and film a water tank.
- Thick resins and roots: vetiver, myrrh, benzoin, patchouli. Fine on a tissue, slow and gummy in a diffuser.
- Absolutes such as rose or jasmine absolute. Solvent-extracted, syrupy and wasted in a tank of water.
- Carrier oils and roll-on blends. Sweet almond, jojoba and anything already diluted for the skin leave the tank greasy.
- Hot spice oils: cinnamon bark, clove, oregano, thyme. Harsh on airways and skin; one drop in a blend, never a fill of their own.
- Fragrance oils. Made to smell like a plant rather than distilled from it; they go in a burner, on reeds or in a machine built for them.
Waterless machines are stricter still: a pod diffuser takes its maker's pods, and a loose oil poured in can void the guarantee. Our rundown of water and waterless diffusers sets out which fill each takes.
Reading the label before you pay
Pure oil and fragrance oil share a shelf and the same brown bottles, so read the back. On a pure oil the ingredient line is the plant itself, Citrus sinensis peel oil for sweet orange, with the part used and whether it was cold pressed or steam distilled, and usually a country of origin and a batch number.
A fragrance oil's ingredient line starts with parfum or a carrier, and the front may say aroma oil or for oil burners. Price is the other clue: rose, jasmine and sandalwood are dear to distil, so any of them at the price of an orange oil is a blend or a fragrance.
How many drops, by type of diffuser
The dose depends on the machine more than on the oil. Water machines dilute it in the tank, nebulisers and pod machines run it neat, and a burner warms a few drops on water. The figures below are the common leaflet ones; the leaflet that came with your machine wins.
| Diffuser | What goes in | Common leaflet figure |
|---|---|---|
| Ultrasonic (water) | Water to the line, oil on top | Three to five drops per 100 ml; start low |
| Nebuliser (cold air) | Neat oil from the bottle | A few millilitres, in short bursts |
| Pod or cartridge machine | The maker's pod or scent bottle | Nothing to measure; set intensity and timer |
| Reed diffuser | A reed base with fragrance | Not for neat oil; it needs a thin base to wick |
Whichever type you run, resist topping up mid-evening; the scent is still there, it is your nose that has moved on. The buying guide on coverage, noise and running cost gives the square-metre figure for each machine, which stops a small bedroom being overdone.
Blends by room and time of day
A blend needs two or three oils at most: something bright on top, something soft or woody underneath. These are starting points many people find pleasant, not rules.
| Room and time | Blend | Why it works |
|---|---|---|
| Kitchen, morning | Lemon with a little rosemary | Bright and clean over breakfast smells |
| Study, daytime | Peppermint and grapefruit | Sharp rather than sweet |
| Living room, afternoon | Sweet orange over cedarwood | The orange lifts, the cedar stays |
| Hallway or bathroom | Eucalyptus with lime | Fresh rather than perfumed |
| Bedroom, evening | Lavender with cedarwood | Soft and low, on the lowest setting |
Keeping the bottles worth using
Heat, daylight and air age an oil, so the shelf beside the hob or a bathroom windowsill is the worst home for it. A drawer in a cool room is better, caps done up straight after use. Citrus goes off soonest, the woods last longest. An oil turned sharp or waxy on the nose is past it; keep it out of the machine.
If you are choosing the machine rather than the oil, our page on picking a diffuser for a bedroom or a hallway matches the types to room size and to how quiet you need it at night.
Sorted the oils, now the machine?
Our buying guide sets water and waterless diffusers side by side on coverage, noise and running cost.