Skatole in Perfumery: Odour, Dosage and Uses
Skatole (3-methylindole, CAS 83-34-1) is an indole that smells faecal at full strength but warm, floral and jasmine-like when heavily diluted. Perfumers use it in trace amounts, often around 0.001% to 0.01% of a formula, to add animalic depth to jasmine, orange blossom, tuberose, civet and leather accords.
Few materials show as clearly how concentration changes a smell. This guide covers what skatole is, why its odour flips with dilution, how perfumers use it, how it compares with indole, and how to handle and buy it.
What is skatole?
Skatole belongs to the indole family and carries a methyl group at position 3 of the indole ring. It forms naturally when the amino acid tryptophan breaks down, which is why it is present in animal faeces. It also occurs in small amounts in flowers such as jasmine, where it contributes to the floral smell at low concentration.
Perfumery skatole is synthetic. One industrial route heats propionaldehyde with phenylhydrazine to form a hydrazone, then cyclises it with zinc chloride or sulphuric acid, a version of the Fischer indole synthesis, according to ChemicalBook. Synthesis gives perfumers a pure, consistent material that would be impossible to extract economically from natural sources.
| Property | Value |
|---|---|
| Chemical name | 3-methyl-1H-indole |
| CAS number | 83-34-1 |
| FEMA number | 3019 |
| Appearance | Almost white to pale brown solid |
| Odour threshold | 0.0000056 ppm |
| Odour family | Musky, indolic, floral |
Data from ChemicalBook.
Why skatole smells different at different strengths
Skatole’s odour threshold is extraordinarily low. ChemicalBook lists 0.0000056 ppm, and a US patent on odour-barrier films cites literature values ranging from 0.02 ppm down to 0.0003 ppb in air. At that sensitivity, even a small amount floods the nose.
ChemicalBook describes the result: a putrid, faecal odour at high concentrations that turns pleasant, jasmine-like, fruity-sweet and warm at very low concentrations. Perfumers therefore treat skatole less as a note in its own right and more as a modifier that adds a sense of something living and warm beneath the main accord.
| Concentration | How it reads |
|---|---|
| Neat or strong solution | Faecal, barnyard, mothball-like |
| Weak dilution | Animalic, leathery, civet |
| Trace in a finished fragrance | Warm, skin-like, deepens jasmine and orange blossom |
How perfumers use skatole
White florals
Jasmine, tuberose and orange blossom accords built only from clean floral materials can smell flat. A trace of skatole, often alongside indole, gives them the slightly heavy, narcotic quality of the real flowers. Typical dosage is 0.001% to 0.01% of the formula.
Animalic and civet bases
Since natural civet is no longer used in mainstream perfumery, civet and musk bases are rebuilt from aroma chemicals. Skatole supplies the faecal-animalic side, often combined with quinolines such as 6 methyl quinoline, which Neshiel lists for artificial civet bases.
Leather, chypre and tobacco
In trace doses skatole adds depth to leather, chypre, tobacco and floral compositions, usually at levels well below 0.01%.
Flavours
Skatole holds FEMA number 3019 and is used at trace levels in some flavour applications, where it adds ripeness. Flavour use requires food-grade material and compliance with local food regulations.
Dosing skatole: a worked example
Because the amounts are so small, perfumers almost never weigh neat skatole into a formula. They work from a stock dilution. Suppose a 100 g fragrance concentrate needs skatole at 0.005%:
- 0.005% of 100 g is 0.005 g, or 5 mg of skatole.
- Weighing 5 mg accurately is difficult, so the perfumer uses a 1% solution instead: 5 mg of skatole is contained in 0.5 g of the 1% solution.
- For finer adjustments, a 0.1% solution means adding 5 g to deliver the same 5 mg.
Common mistakes are overdosing when a formula is scaled up from a lab trial, forgetting that skatole is already present in some natural jasmine materials in the formula, and evaluating on a blotter too soon. Skatole’s character shifts as the fragrance dries down, so judge it after several hours and again on skin.
Skatole vs indole
| Factor | Skatole | Indole |
|---|---|---|
| Structure | Indole with a methyl group at position 3 | Parent indole ring |
| CAS | 83-34-1 | 120-72-9 |
| Odour | More faecal and animalic | Floral-indolic, mothball-like when strong |
| Strength | Higher impact, used at lower dosage | Used at somewhat higher dosage in floral accords |
| Main role | Animalic modifier | Core of jasmine and orange blossom accords |
Both occur in civet, and both are present in white flowers. Perfumers often use them together, with indole carrying the floral body and skatole adding warmth.
Working with skatole safely
- Always work from dilution. Weigh skatole in milligrams and prepare 1% or 0.1% solutions in a suitable solvent for formulation and evaluation.
- Prevent contamination. Use dedicated spatulas, pipettes and glassware. A trace on a shared tool will show up in other compositions.
- Store sealed, cool and dark. Indoles can discolour on exposure to air and light. Amber glass and tight closures help.
- Follow the SDS. Skatole is biologically active: research has linked one of its metabolites to lung damage in cattle. Wear gloves and eye protection and work with ventilation.
- Check IFRA guidance for the product categories you are formulating.
Buying skatole
- Purity of 98% or higher by GC is the usual benchmark for perfumery grade.
- Ask for colour on the certificate of analysis; darker material may have oxidised.
- Evaluate odour from a dilution against your approved reference.
- Buy pack sizes that match your consumption. Because dosage is tiny, even large fragrance houses use small quantities, and fresher stock smells cleaner.
For a wider view of the materials skatole is used alongside, read our aroma chemicals list.
Looking for perfumery-grade skatole or quinolines for civet and leather bases? Contact Neshiel for samples and pricing, or browse our flavours and fragrances range.
Frequently asked questions
What does skatole smell like?
Faecal and barnyard-like when concentrated, and warm, floral and jasmine-like when very dilute.
Why is skatole used in perfume?
At trace levels it adds animalic depth and warmth, making white floral and leather accords smell more natural.
Is skatole natural?
It occurs naturally in jasmine, orange blossom and civet, but the skatole used in perfumery is synthesised for purity and consistency.
How much skatole goes into a perfume?
Typically around 0.001% to 0.01% of the formula, and often less.
Is skatole the same as indole?
No. Skatole is 3-methylindole, a methylated form of indole, and it smells more faecal and animalic.