Fragrance allergens / alpha-Isomethyl Ionone
alpha-Isomethyl Ionone
alpha-Isomethyl Ionone must be declared in the EU, Northern Ireland and Great Britain once it crosses the threshold.
Identity
| Name in the ingredient list | alpha-Isomethyl Ionone |
|---|---|
| CAS / EC number | 127-51-5 / EC 204-846-3 |
| EU Annex III entry | 90 |
| GB Annex III entry | 90 |
It is one of the long-standing entries, carried unchanged through the 2023 expansion.
When it must appear on the label
alpha-Isomethyl Ionone may be present as a constituent of essential oils or fragrance compounds. It must be named individually in the ingredient list when its total concentration in the finished product exceeds 0.001% in leave-on products (lotions, balms) or 0.01% in rinse-off products (soap, shower gel), summed across every fragrance source in the recipe. Below the threshold it stays within the collective term "Parfum".
United States: no individual fragrance-allergen labelling is in force yet (MoCRA rulemaking pending); fragrance is declared collectively as "Fragrance".
Common questions
Do I have to list alpha-Isomethyl Ionone on my label?
alpha-Isomethyl Ionone must be declared in the EU, Northern Ireland and Great Britain once it crosses the threshold. It must be named individually once it exceeds 0.001% of a leave-on product or 0.01% of a rinse-off product, summed across every fragrance source in the recipe. Below that it stays inside the collective term "Parfum".
What is the CAS number for alpha-Isomethyl Ionone?
alpha-Isomethyl Ionone is listed under CAS 127-51-5 (EC 204-846-3), Annex III entry 90.
Tell me if alpha-Isomethyl Ionone changes
alpha-Isomethyl Ionone is declarable in the EU, Northern Ireland and Great Britain today. Those lists diverge, and they have both moved before. If alpha-Isomethyl Ionone's entry changes on either list, we update the rule tables and email you.
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Sources
- Regulation (EC) No 1223/2009, Annex III (consolidated text of 18.05.2026), entries 67 to 92 (EUR-Lex)
- Assimilated Regulation (EC) No 1223/2009, Annex III, as it applies in Great Britain, entries carrying the individual-declaration condition (legislation.gov.uk)
Transcribed from the official texts linked above and checked against them; a labelling reference, not safety advice. You remain responsible for your product's labelling.
Rule tables last checked 25 September 2026.