What it does
CosIng, the EU's cosmetic ingredient database, lists three functions for limonene: perfuming, solvent and deodorant.1 Market surveys reviewed by the EU's Scientific Committee on Consumer Safety (SCCS) found limonene and linalool to be the fragrance chemicals most commonly used in cosmetics. Outside cosmetics, limonene is also used as a solvent in technical and cleaning products.2
Where it comes from
Limonene is the main component of citrus oils2, and the peel oil of citrus fruits is largely R-(+)-limonene.3 It exists in two mirror-image forms, R-(+)- and S-(-)-limonene, and an equal mixture of the two is known as dipentene.2
On a label all of these are simply Limonene: since 2023 one Annex III entry covers d-, l- and dl-limonene under that name.4
What EU rules require
Annex III entry 88 requires limonene to be named in the ingredient list when it exceeds 0.001% in leave-on or 0.01% in rinse-off products. The same entry says the peroxide value of each form must be below 20 mmol/L, a limit that applies to the substance used, not to the finished product.5 The peroxide content stands for the oxidised fraction of the substance.2
Like the other named fragrance allergens, the labelling is there so that people already allergic to limonene can find it on a pack.4
As a pure substance, limonene's EU harmonised classification lists it as flammable, a skin irritant, a skin sensitiser and hazardous to the aquatic environment.6 That describes the concentrated liquid, not a product that contains a small amount of it.
Oxidation: what sources say
The SCCS reports that limonene's allergenicity is closely related to oxidation: both of its forms oxidise spontaneously in air, and the primary oxidation products, hydroperoxides, are strong and clinically relevant contact allergens.2
In a patch-test study in six countries, oxidised R-limonene with a set hydroperoxide content of 0.33% gave positive reactions in 5.2% of 2,900 consecutive dermatitis patients, ranging from 2.3% to 12.1% between clinics. The authors describe pure limonene as not allergenic, or a very weak allergen.7 The authors add that many of these patients would not have learned of their fragrance allergy without this specific test7, and an earlier study at four European clinics found that 57% of those reacting to oxidised limonene did not react to fragrance mix or balsam of Peru.3 In both studies these were people referred for patch testing, not the general population.
Linalool, the other fragrance chemical the surveys found most often, follows the same pattern: the SCCS notes that the non-oxidised substances rarely cause allergic reactions, while oxidised limonene and oxidised linalool rank among the most common contact allergens.2
How it appears on a label
As Limonene, usually near the end of the list after Parfum. Because citrus oils are mostly limonene, it can appear next to a citrus ingredient such as Citrus Limon Peel Oil or Citrus Aurantium Bergamia Peel Oil, both of which have been named fragrance allergens in their own right since 2023.4
If you know you react to limonene, look for its name; a list that says only Parfum cannot confirm it is absent. See EU fragrance allergen labels and fragrance free vs unscented.