What is limonene in skincare and fragrance?

What limonene is

We work from documents; we have not tested any products. The US National Library of Medicine’s PubChem record for limonene (retrieved 2026-11-14) describes it as “a monoterpene that is cyclohex-1-ene substituted by a methyl group at position 1 and a prop-1-en-2-yl group at position 4.” Its entry also says that (+/-)-limonene is “a natural cyclic monoterpene and major component of the oil extracted from citrus rind.” DermNet NZ puts it in fragrance terms: “fragrance chemicals extracted from the peel of citrus fruits (limonene) and herbs, flowers, and woods (linalool).”

Names you may see

PubChem lists CAS registry numbers 138-86-3 and 7705-14-8 for the record, and synonyms including dipentene, cinene, cajeputene, DL-Limonene and kautschin. Its description of dipentene says it “appears as a colorless liquid with an odor of lemon.” We did not find a source for the name used on cosmetic ingredient lists, so we do not say which spelling to look for there. Our guide to fragrance allergen names on ingredient labels covers the label side more generally.

Where it occurs, as the sources say

DermNet says limonene is extracted from citrus peel, and PubChem’s description refers to the oil extracted from citrus rind. PubChem also says (+/-)-limonene “has been reported in Camellia sinensis, Hypericum foliosum, and other organisms with data available,” and that it is a metabolite found in or produced by Saccharomyces cerevisiae. We have nothing further on which plants or products contain it.

Outside cosmetics, a 1997 PubMed abstract (PMID 9165203, Contact Dermatitis 1997) says d-limonene, “obtained as a by-product from the citrus juice industry,” was introduced as a defatting and cleaning agent. PubChem’s description of dipentene says it is used as a solvent for rosin, waxes and rubber, and in floor waxes and furniture polishes. A 2019 PubMed abstract (PMID 31433385, Dermatitis 2019) calls limonene “a fragrance widely used in cosmetics and household products.” A review in PubMed Central, Contact allergy to fragrances: current clinical and regulatory trends, calls limonene and linalool “the most commonly used fragrance terpenes.” A second review, What is New in Contact Allergy To Cosmetics, says the non-oxidised forms “are the most common fragrances used in cosmetics and consumer products.” The first review adds that in tests which looked at product ingredient declarations, limonene and linalool were the most frequently identified substances.

Why it comes up: oxidation

DermNet says limonene is itself an occasional contact sensitiser. It adds that “on exposure to oxygen in the air, both substances oxidise into hydroperoxides which are much more potent sensitisers,” and that they are “an increasingly recognised source of allergic contact dermatitis.”

The second review uses the term prehapten. A hapten is “a sensitizing chemical that can penetrate the skin and bind directly to the protein, resulting in contact allergy.” Limonene is described as a prehapten: the substance itself is non- or low-allergenic, but after air-oxidation its hydroperoxides are “much more allergenic.” The first review reports that in animal experiments the oxidation products of terpenes such as limonene were “markedly more potential allergens than the nonoxidized raw substances.” It adds that oxidation can be delayed by antioxidant agents, which it says must be monitored because they can themselves cause allergies.

The PubMed abstracts report the same pattern in patch-test studies, and we describe them as findings of those studies only:

• One abstract (PMID 31433385) says contact allergy to limonene was long considered rare, then that hydroperoxides formed on exposure to air were found to have “a far stronger sensitizing potency than the pure compound.” It also cautions that a number of “positive” reactions “may well be false-positive, irritant responses.”
• A Spanish study of 3639 consecutive patients (PMID 27896835, Contact Dermatitis 2017) reports positive patch-test reactions to limonene hydroperoxides in 1.4%, 3.4% and 5.1% of patients at three test concentrations.
• A retrospective US study (PMID 28885310, Dermatitis 2017) reports positive reactions to the hydroperoxides of D-limonene in 8% (7/90) of patients with suspected fragrance allergy. It tested 103 patients in total.
• The 1997 abstract (PMID 9165203) reports that oxidised d-limonene gave positive patch-test reactions at a proportion it describes as comparable to several allergens in the standard series.

These studies tested selected patient groups in clinics, so none of them tells you how common the allergy is in the general population.

What a label can and cannot show

A review on patch testing, Fragrance Contact Allergy: A Review Focusing on Patch Testing, says it is “difficult to know whether a prehapten has altered to a hapten(s) before skin contact,” and that it is “impossible to establish positive clinical relevance exclusively by assessing the ingredient labels.” Chemical analysis would be needed to measure the oxidation products.

The other review is more cautious about the evidence. It says the degree of exposure to the oxidised forms “is insufficiently established,” that the amount reported in cosmetics “can rarely elicit a skin reaction,” and that, because the whole chain of evidence is lacking, such allergies are often deemed to have unknown relevance. We report both statements as the reviews’ wording. Together they say that allergy to limonene hydroperoxides is recognised in testing, while how much it matters in everyday products is not settled in what we read.

What the EU regulation text says

The excerpts we kept from Commission Regulation (EU) 2023/1545 (retrieved 2026-11-14) do not name limonene, so we make no claim about its specific entry. What they do say is general. The regulation amends Regulation (EC) No 1223/2009 “as regards labelling of fragrance allergens in cosmetic products,” and states that “fragrance substances, such as prehaptens and prohaptens, that can be transformed to known contact allergens via air oxidation or bioactivation should be treated as equivalent to fragrance allergens.” It also says perfume and aromatic compositions are to be referred to as “parfum” or “aroma” in the list of ingredients, complemented by the allergens whose mention is required. For how that works, see what is parfum, how to read an ingredient list for parfum and aroma and the EU fragrance allergen list, explained.

The US labelling point

The FDA’s Fragrances in Cosmetics page (retrieved 2026-11-11) says: “under U.S. regulations, fragrance and flavor ingredients can be listed simply as ‘Fragrance’ or ‘Flavor.’” So a list that names limonene shows one thing; a list that says only “Fragrance” may not. The same page says even some products labeled “unscented” may contain fragrance ingredients. See fragrance-free vs unscented and why “fragrance” hides ingredients.

How this site treats it

On this site, a product whose maker’s published ingredient list names limonene is flagged by our watch list. That is our own editorial rule for a site about avoiding fragrance chemicals. It is not a regulation, and no source we read says limonene must be avoided by everyone. DermNet’s page does advise avoiding products that contain the parent allergen, but that is a statement for people with a diagnosed allergy and we pass it on as the source’s wording only. The same approach applies to the neighbouring chemical in what is linalool, and the wider topic is in what is natural fragrance.

A plain line about fragrance

Fragrance ingredients are not inherently harmful, and this site is not against them. The issue is narrower: what labels tell people who react to fragrance. For questions about your own reactions, ask a clinician, or look to an allergy or dermatology society. The sources above discuss patch testing; whether it suits you is a medical question.

What we don’t fully know

We found no source for the label name of limonene. The EU text we kept does not name limonene, so we say nothing about its labelling thresholds or limits. We cannot say which household or cleaning products contain limonene, or how much oxidised limonene any product holds. The full list is under “unknowns” on this page.