Material guide · 96
Material guide: para-cresol, what the forum probably means when it calls ylang ylang faecal
· 17 min read
CAS 106-44-5, 25 suppliers. The database's recommended evaluation strength is 0.10 percent or less, the lowest band in the whole library. The odour field reads phenolic, narcissus, animal, mimosa. It is recorded in cananga oil from China at 0.27 percent, cananga being the same genus as ylang, and it also turns up in coffee, butter, blackcurrant buds and oolong tea. The toxicity field is what makes it worth an entry: rat oral LD50 207 mg/kg and rabbit dermal 301 mg/kg, where ylang ylang essential oil itself reads greater than 5000 for both. Same plant, and the constituent sits more than 24 times below the whole oil. Substantivity 400 hours; melting point 32 to 35 C, so it crosses back and forth around room temperature.
In short: a phenolic material the database wants evaluated at 0.10% or less, which reads as narcissus and mimosa diluted and animalic neat. It earns an entry by demonstrating that the toxicity numbers for a plant oil and for one of its constituents can sit two orders of magnitude apart.
Fields
| Field | Value |
|---|---|
| CAS | 106-44-5 |
| First synonym | 4-hydroxytoluene |
| Formula | C7H8O, MW 108.140 |
| Database category | cosmetic, flavor and fragrance agents |
| Appearance | white crystals (est) |
| Assay | 98.00 to 100.00 |
| Melting point | 32-35 C |
| Boiling point | 201.8-202.0 C @ 760 mmHg |
| Flash point | 89.44 C |
| logP | 1.90 (est) |
| Vapour pressure | 0.110 mmHg @ 25 C |
| Water solubility | 21,500 mg/L @ 25 C (measured) |
| Odour type | phenolic |
| Odour | phenolic; narcissus; animal; mimosa |
| Strength | high, recommend smelling in a 0.10% solution or less (rank 3) |
| Substantivity | 400 hours (10% in dipropylene glycol) |
| Occurrence | cananga oil, China @ 0.27%; coffee bean; butter; blackcurrant bud; asparagus; anise; blueberry; sour cherry; sea algae |
| Suppliers | 25 |
| Regulatory | JECFA 693, FEMA 2337, CoE 619, FLAVIS 04.028 |
| Cosmetic uses | antimicrobial agents; perfuming agents |
| Oral toxicity | rat LD50 207 mg/kg; mouse 344 |
| Dermal toxicity | rabbit LD50 301 mg/kg; rat 750 |
| GHS | H301 Toxic if swallowed; H311 Toxic in contact with skin; H314 Causes severe skin burns and eye damage; H411 Toxic to aquatic life with long lasting effects |
Two orders of magnitude
Somebody on the forum described ylang like this.
"Ylang ylang stinks to high heaven, it has a strong poop nuance." (Tiny-Education3316)
That description points at phenolics. And in the database's occurrence field, para-cresol is listed in cananga oil from China at 0.27%. Cananga and ylang ylang are the same genus.
Setting the constituent's toxicity beside the whole oil's:
| Rat oral LD50 | Dermal LD50 | |
|---|---|---|
| Ylang ylang flower oil | > 5000 mg/kg | rabbit > 5000 mg/kg |
| para-cresol | 207 mg/kg | rabbit 301 mg/kg |
More than 24-fold apart orally, more than 16-fold dermally.
The GHS field is blunter. Ylang ylang flower oil carries H315 (skin irritation) and H317 (may cause an allergic skin reaction). Para-cresol carries H301 (toxic if swallowed), H311 (toxic in contact with skin) and H314 (causes severe skin burns).
That is not a contradiction, it is concentration. A constituent at 0.27% is diluted by the other 99.73%.
Two directions worth keeping. Somebody buying a whole essential oil gets a pre-diluted version; somebody buying the isolate gets it neat. And running the other way, a natural label does not guarantee that everything inside is mild.
(On why ylang is restricted, what I saw while searching pointed at constituents such as isoeugenol rather than para-cresol. This section is a general point, not an account of that restriction.)
That 0.10% field
Recommended evaluation strength: 0.10% or less.
That is the lowest band across the ninety-odd materials I have written up. For comparison: ambroxan 1%, rose oxide 1%, ethyl maltol 5%, amber naphthofuran 10%.
And the odour field carries "animal" alongside "narcissus" and "mimosa". Those two groups look mismatched, and the difference is concentration. The database's odour description records the state at 0.10% in dipropylene glycol: phenolic, narcissus, animal, mimosa.
What it is like neat, that field does not record.
Melting point 32 to 35 C
White crystals, melting between 32 and 35 C.
That is near body temperature, and within reach of an indoor summer. This material moves between solid and liquid on your shelf. Harmless in itself, but it explains why most people buy it pre-diluted: 8 of its 13 corpus appearances are tagged 10% or 1%.
(Several articles back I wrote that a co-solvent's own melting point matters if it lands in the room-temperature range. Here the same thing shows up on an active material.)
The antimicrobial field
Cosmetic uses reads "antimicrobial agents; perfuming agents".
Phenolics having antimicrobial activity is old knowledge, and what this field is a reminder of is that the material is not only contributing odour in a formula. At what concentration the antimicrobial effect appears, and how far that is from perfumery levels, I did not look into.
Corpus
Across 954 published formulas, para-cresol appears in 13, or 1.4%.
By spelling: para-cresol 5 times, para-cresol 10% 5 times, para-cresol 1% 3 times. More than 80% of uses are dilutions.
Median dose 0.700%, 90th percentile 5.000%, maximum 5.31%.
Most of those figures are doses of a dilution rather than of the neat material. In the five tagged 10%, the actual neat material is a tenth of the listed value.
In the same corpus ylang ylang appears in 159 formulas (16.7%) and jasmines in 101 (10.6%).
Why it turns up in an ylang thread
Somebody on the forum mentioned Canada.
"RIP to the Canadian perfumers who can't use ylang ylang in commercial formulations anymore due to the P-creosol ban lol" (Hoshi_Gato)
I cannot verify the current state of Canadian regulation; it is not in this database. What is verifiable is the first half of the thread: para-cresol is recorded in an oil of this genus, and it is a molecule carrying acute-toxicity GHS statements.
When a natural complex material gets restricted, the reason often sits in one constituent rather than in the oil itself. de Groot and Schmidt's 2017 Dermatitis paper titled "Sandalwood Oil, Ylang-Ylang Oil, and Jasmine Absolute" is built on exactly that structure: contact allergy to these materials, and the ingredients responsible for it.
In Geier and colleagues' IVDK data in Contact Dermatitis in 2022, ylang ylang (I + II) oil had the highest patch-test positive rate of twelve essential oils at 3.9%. That paper tested oils, not constituents.
What this doesn't establish
- I have not smelled it. This is database fields plus two papers.
- The 0.27% is one figure for cananga oil from China. The database gives no para-cresol content for the ylang fractions, and fractionation changes composition.
- I did not verify the state of Canadian regulation. On that forum comment, all I confirmed is that para-cresol occurs in an oil of this genus.
- I did not verify what drives ylang's IFRA restriction. What I saw pointed at isoeugenol, unverified, and that is a different molecule.
- The toxicity sources are old (BIOFAX 1969) and are animal acute toxicity, which does not extrapolate directly to human skin contact.
- The "24-fold" is a ratio of two LD50s, and the ylang figure is a greater-than lower bound, so the real gap can only be larger. That direction needs stating.
- I did not look up the antimicrobial concentration.
- Thirteen formulas is too few. The dose statistics are indicative at best, and they mix dilutions with neat material.
- I did not describe the neat odour, because the database's odour description stops at 0.10% in dipropylene glycol.