Material guide · 126
Material guide: camphor — its odour field holds one word, and that word is its own name
· 18 min read
CAS 76-22-2, 66 suppliers, FEMA 4513. Its odour type is camphoreous, its odour field is camphoreous, its flavour field is camphoreous and its taste description is camphoreous — four fields, one word, and that word is the material's own name. It has no strength field and no substantivity field. Its cosmetic_uses reads denaturants, fragrance, plasticisers. And it is one of the few materials here with data on all three toxicity routes — oral, subcutaneous, and the inhalation route that only 6.6% of records carry. Xu 2005 showed in J Neurosci that camphor activates and strongly desensitises TRPV1, at a site distinct from capsaicin's — which is how it works as a topical analgesic.
About 5 minutes.
Short version
- Name: (±)-camphor (DL-camphor), CAS 76-22-2, C10H16O
- FEMA 4513, CoE 140; assay 96.00 to 100.00
- Odour type camphoreous, odour camphoreous, flavour camphoreous, taste camphoreous
- No strength field and no substantivity field
- Melting point 176–177 °C, a white crystalline solid; vapour pressure 0.65 mmHg, high for a solid
cosmetic_uses: denaturants; fragrance; plasticisers- Suppliers: 66
- Data on all three toxicity routes, including the inhalation route only 6.6% of records carry
Four fields, one word
This record does something I have not seen elsewhere:
| Field | Content |
|---|---|
odor_type |
camphoreous |
odor |
camphoreous |
flavor_type |
camphoreous |
flavor |
camphoreous |
taste_descriptions |
camphoreous |
Five fields, one word, and that word is the material's own name.
This is not a data gap; it is a peculiar kind of completeness. Camphor defines its odour family — "camphoreous" as a descriptor means "smells like camphor". It cannot describe itself in other words, because other things are described using it.
(For contrast, nerolidol's odour field holds five words and angelica root oil's holds eleven.)
And it has neither a strength nor a substantivity field. Those two are filled in on nearly every record in this series — I have measured the substantivity ceiling and the strength-rank distribution. This one leaves both blank.
Two of its three uses are not perfumery
The cosmetic_uses field:
denaturants; fragrance; plasticisers
Denaturant came up with methyl salicylate — something added to alcohol to make it undrinkable. Camphor is another.
Plasticiser is new. Camphor was historically the plasticiser for celluloid, one of its earliest large-scale industrial uses.
So of this material's three cosmetic uses, only one is about smell.
It carries a Vicks conversion
The formulations field holds a concrete conversion that is rare in this database:
twenty grams of Vicks VapoRub, 10 ml of Campho-Phenique, and 16 ml of Vicks VapoSteam each contain about 1 g of camphor.
That is a statement converting consumer products into material weight. Most formulations fields list grades (technical, USP); this one lists something a reader can check against their bathroom cabinet.
It also lists pharmaceutical preparations, such as camphor spirit at 10% in alcohol.
One of the few materials with all three routes
Last time I measured coverage across the three toxicity fields: among materials with ten or more suppliers, oral 51.7%, dermal 31.2%, inhalation only 6.6%.
Camphor has all three:
| Route | Data |
|---|---|
| Oral | mouse LD50 1310 mg/kg; child TDLo 51 mg/kg: somnolence, convulsions |
| Subcutaneous | rat LD50 70 mg/kg; frog LDLo 240 mg/kg |
| Inhalation | mouse LCLo 400 mg/m³ over 3 hours: muscle contraction or spasticity |
That child entry is one of the 156 human toxicity records I collected, and 51 mg/kg is at the low end of that list.
The subcutaneous 70 mg/kg needs care too — that is injection under the skin, not application to it, which are different things. But it is a low figure for this database.
(As always: these are ingestion, injection and inhalation experiments, separated from a perfume's dermal dose by route and by amount. Camphor's dermal route has a more relevant paper, below.)
It activates capsaicin's channel
Xu and colleagues addressed a basic question in the Journal of Neuroscience in 2005: camphor has long been used as a topical analgesic, and nobody knew its molecular mechanism.
Their opening sets the context:
Capsaicin and menthol, two other topically applied agents widely used for similar purposes, are known to excite and desensitize sensory nerves by acting on two members of the transient receptor potential (TRP) channel superfamily: heat-sensitive TRPV1 and cold-sensitive TRPM8, respectively.
And their finding:
Camphor has recently been shown to activate TRPV3, and here we show that camphor also activates heterologously expressed TRPV1, requiring higher concentrations than capsaicin. Activation was enhanced by phospholipase C-coupled receptor stimulation mimicking inflamed conditions. … Camphor activation of rat TRPV1 was mediated by distinct channel regions from capsaicin.
And the paper's title carries the second half: camphor activates TRPV1 and strongly desensitises it.
Activate, then stop responding — that is the topical analgesic mechanism.
This fills in another square on the temperature-receptor line. This series already has menthol (TRPM8, cold), cinnamaldehyde (TRPA1), eugenol and WS-3 (pure cooling, trigeminal). Camphor adds TRPV1 — capsaicin's heat channel, entered through a different door.
Its dermal absorption has a number
Martin and colleagues' 2004 measurement of camphor, menthol and methyl salicylate is one I cited under methyl salicylate (same study; here I am reading the camphor column).
Eight subjects, eight commercial patches, eight hours:
| Plasma Cmax | |
|---|---|
| Camphor | 41.0 ± 5.8 ng/mL |
| Menthol | 31.9 ± 8.8 |
| Methyl salicylate | 29.5 ± 10.5 |
Camphor is the highest of the three. And the paper's opening says why the measurement was needed: despite extensive use, there had been no estimates of human exposure following dermal application.
How to use it
- It is a crystalline solid melting at 176–177 °C. Weigh it and make a solution; the solubility field lists alcohol.
- But it sublimes. A vapour pressure of 0.65 mmHg is high for a solid melting at 176 °C — it will leave slowly if you let it. Keep it sealed.
- With no strength or substantivity field, you have to measure it yourself. There is nothing to reference for dose.
- It will set the direction of a whole composition. "Camphoreous" is a hard signal to hide.
- Note that it is also a denaturant and a plasticiser — if your alcohol smells of camphor, you may not have put it there.
What this doesn't establish
- I have not smelled it. The whole article is fields, database-wide counts and two papers.
- Xu's work is a heterologous expression system and rat dorsal root ganglion neurons, not human perception. I note that TRPV1 activation needs higher concentrations than capsaicin without repeating the ratio.
- Martin 2004 used commercial patches, not perfume — patches are engineered to promote absorption, so 41.0 ng/mL does not transfer to something sprayed on skin. I noted this under methyl salicylate too.
- The child TDLo of 51 mg/kg is ingestion data, and the effects include convulsions. I have not converted it into any dermal or inhalation dose.
- The subcutaneous and inhalation data are from 1934 and 1957, with methods unlike modern standards.
- "Four fields, one word" describes this record. I did not count how many materials database-wide have a single-word odour field.
- The Vicks conversion carries no date or source, and consumer formulations change.
- I did not check the current IFRA standard for this material.