Short answer
Many fragrance oils sold to small brands are not 100% fragrance: they are cut with a carrier such as dipropylene glycol (DPG), isopropyl myristate (IPM), triethyl citrate or benzyl benzoate, to make them cheaper, easier to pour or more consistent. The supplier's documents rarely say so plainly, so ask directly what percentage of the oil is solvent and which one. It matters for three things: how strong your product really is, whether the carrier mixes with your base, and what ends up on your label. Restriction limits on the supplier's IFRA certificate already apply to the oil as supplied, carrier included.
Why oils are sold diluted
A fragrance compound straight from its maker can be thick, very strong and expensive. Diluting it before resale lowers the price per kilogram, makes it pour and blend more easily, and standardizes its strength. None of this is improper, as long as the buyer knows. The problem is the buyer who does not: two "fragrance oils" used at the same 20% may contain very different amounts of fragrance.
How to tell
The only reliable answer comes from the supplier. Ask, in writing:
- Is the oil supplied neat, or diluted? If diluted, in what and at what percentage?
- Is it suitable for alcohol-based perfume, for oil-based products, or for candles only?
- Does the IFRA certificate refer to the oil exactly as supplied?
- Is any carrier also a declarable allergen or a restricted material?
Clues you can check yourself, none of them conclusive:
- The safety data sheet. Section 3 lists hazardous components above set thresholds; non-hazardous solvents may not appear at all. A composition that adds up to well under 100% leaves room for a carrier.
- Odor strength. An oil that smells much weaker than a similar oil from another supplier may be more diluted.
- Behavior in alcohol. A small test dilution in perfumer's alcohol that turns hazy suggests an oily carrier such as IPM, which does not mix well with high-strength ethanol.
- Product positioning. Oils sold primarily for candles and soap are more often diluted, and with carriers chosen for those uses.
The documents themselves are explained in fragrance material SDS and specifications.
The arithmetic
If an oil is 50% fragrance in DPG, every gram of it carries 0.50 g of fragrance and 0.50 g of DPG. Used at 15% in a 100 g perfume:
- fragrance oil as supplied: 15.00 g — the figure most people would call the concentration;
- fragrance material: 15.00 × 0.50 = 7.50 g, or 7.5% of the perfume;
- DPG: 7.50 g, which stays in the perfume because it hardly evaporates.
The "15%" perfume contains half as much fragrance as a perfume made with a neat oil at 15%. To match the neat version's strength you would use the diluted oil at 30% — and the perfume would then contain 15% DPG. This is the same distinction between a row's weight and its pure active that runs through formula %, absolute % and relative %; record the oil with its known dilution, as you would any diluted material.
What the carrier does to your product
| Carrier | In alcohol perfume | In oil-based products | Worth knowing |
|---|---|---|---|
| DPG | Mixes; adds a slightly sticky, non-evaporating fraction | Mixes poorly with many carrier oils | Nearly odorless |
| IPM | Can haze at high ethanol strength | Mixes well | Oily feel |
| Triethyl citrate | Mixes | Variable | Low odor |
| Benzyl benzoate | Mixes | Mixes | Also a fragrance material and an EU-listed allergen; it counts toward declarations |
A carrier that suits candle wax may be wrong for a skin product, and vice versa. If you make oil-based perfumes, see oil-based perfume concentration for why DPG-cut oils can separate in triglycerides.
IFRA certificates and labels
An IFRA certificate for a fragrance oil states the maximum percentage of that oil, as supplied, in each product category. If the oil is 50% DPG, the certificate's limits already account for that, so you compare your use level of the oil directly with the certificate — no adjustment. Do not "correct" a certificate's figure for the carrier; you would double-count it. Reading certificates is covered in how to read an IFRA certificate.
On a label, the carrier is part of the fragrance only if it serves as part of the fragrance. Rules differ by market, and a carrier that is also an allergen (benzyl benzoate) may need declaring by name above the threshold where allergen labeling applies. Ask your supplier for an allergen statement covering the oil as supplied, and see perfume ingredient labeling.
Recording a purchased oil
- Record the oil with its carrier and dilution as stated by the supplier, and the date you were told.
- File the supplier's answer with the SDS, IFRA certificate and allergen statement.
- If the supplier will not say, record "dilution unknown" — not "neat".
- Re-ask when you change supplier or the supplier changes the product.
RUŌOD Lab records a material's dilution on each formula row and can flag a material as a solvent, so a known-dilution oil contributes the right amount of pure fragrance to every percentage. The broader arithmetic is in the perfume dilution and calculations guide.
Frequently asked questions
Is a diluted fragrance oil worse?
Not necessarily — you are paying for less fragrance, and the carrier may be unsuited to your product, but the fragrance itself can be identical. What matters is knowing.
My supplier says the oil is "100% fragrance". Can a solvent still be in it?
Some compounds contain solvents as part of the fragrance formula itself — the perfumer used them in the composition. That is different from cutting the finished oil. Ask whether any solvent was added after compounding.
Written and reviewed by the RUŌOD Lab team. This article is general education about perfume formulation and record-keeping; it is not legal, regulatory or safety advice, and the examples are illustrations, not validated commercial formulas. How we write and check these guides.