Fragrance allergen

alpha-Isomethyl ionone

Alpha-isomethyl ionone is a violet and iris-type fragrance ingredient from the methyl ionone family. It gives a powdery floral effect and is made by chemical synthesis. Perfumers use it in floral and woody blends and in soap perfumes. It is also listed as a flavouring ingredient.

Formula
C14H22O
Molar mass
206.33 g/mol
CAS
127-51-5

Where it comes from

Commercial material is made in a factory, not pressed or distilled from plants. One supplier describes reacting citral with methyl ethyl ketone under alkaline conditions, followed by acid treatment to form a mixture of methyl ionone isomers. PubChem records one plant report, in the magnolia species Magnolia kobus.

Smell and use

Violet-like, sweet and powdery, with an orris feel and a woody undertone.

It builds violet, iris and orris effects, and is used in floral and woody blends, ylang-ylang and leather notes, amber and chypre accords, and soap perfumes. Outside perfume, it is listed in the JECFA flavourings index as a flavouring agent.

On the label

Named on 39% of the 6,851 perfume ingredient lists we hold (2,663 perfumes).

EU
Annex III, entry 90. Must be named above 0.001% in leave-on products (0.01% rinse-off).
Great Britain
Required, same thresholds. GB Annex III

The SCCS opinion SCCS/1459/11 lists it among established contact allergens in humans, and it was already regulated under Annex III. IFRA has a Restriction standard covering methyl ionone mixed isomers, which includes this CAS number. Most company notifications to ECHA include the H317 skin sensitiser statement. EU rules require it to be named on labels above set thresholds.

A list that does not name it does not prove it is absent: brands only have to name it above the threshold.

Frequency by concentration

  • Eau de parfum 37% of 4,889
  • Eau de toilette 46% of 1,227
  • Extrait 25% of 341
  • Parfum 61% of 194
  • Cologne 33% of 114
  • Body spray 26% of 42
  • Other 30% of 27

Share of the perfumes we hold a list for, in each concentration.

Named alongside

Share of the lists naming alpha-Isomethyl ionone that also name each of these.

Notes whose materials include it

Perfumes whose box names it

Common questions

What does alpha-isomethyl ionone smell like?

It smells of violet and orris, sweet and powdery, with a woody undertone, according to one supplier's odour listing. Another supplier describes a dry, powdery scent with a violet-sweet quality.

Is alpha-isomethyl ionone natural or synthetic?

Commercial material is synthetic, according to a supplier. The supplier describes reacting citral with methyl ethyl ketone, then closing the ring with acid to give the methyl ionone isomers. PubChem records one plant report, in Magnolia kobus.

Why is alpha-isomethyl ionone on my perfume label?

It is on the EU list of fragrance allergens that must be named in the ingredient list, alongside 'parfum'. The trigger is 0.001 per cent in leave-on products or 0.01 per cent in rinse-off ones.