That long name on the label: alpha-isomethyl ionone
Arin Editorial · how this is made
You may see 'alpha-isomethyl ionone' on the ingredient list of a perfume, deodorant or moisturizer. It is a synthetic fragrance ingredient. Why does this unremarkable name get its own line on the label?
What is it and where does it show up?
Alpha-isomethyl ionone is a synthetic fragrance ingredient used in cosmetics. It can appear in perfumes, eau de toilette, aftershaves, deodorants, soaps, shampoos, hair dyes and creams. In some formulas it is also listed for keeping the skin in good condition, but its main job is scent.
What does it do?
It improves the smell of a product and leaves fragrance on the skin. Its secondary function is described as helping keep the skin in good condition.
Why is it listed separately?
The EU cosmetics regulation puts this ingredient on Annex III, its fragrance allergen list. Above a certain concentration it must be named separately on the label. That separate listing does not mean the ingredient is banned; it is a rule meant to help allergic consumers recognize the product. The SCCS has also addressed it in opinions on fragrance allergy.
What do the data say?
Skin irritation records differ by species: no significant irritation in rabbits, severe irritation in rats. One human study recorded a high frequency of skin sensitization. These are compiled records; they do not settle anything without looking at dose and exposure route. Laboratory screens for estrogen receptor activity found no significant effect, but that alone does not prove there is no hormonal effect in real use.
In the European Union it is restricted under Annex III of Regulation (EC) No 1223/2009 and must be listed separately above certain thresholds.
If you do not have a known fragrance allergy, there is no warning telling you to avoid this ingredient. If a perfumed product makes your skin red, itchy or eczematous, stop using it and see a dermatologist. If you know you are allergic, seeing this name on a label is a good reason to skip the product.
Sources
- EU Regulation (EC) No 1223/2009, Annex III
- SCCS opinions on Fragrance Allergy
- EPA ToxCast / ToxValDB records