Limonene is the main citrus terpene: the compound that gives lemon, orange and other citrus peel its fresh smell. It also occurs in hemp, cannabis, mint and juniper, and is widely used as a fragrance and as a solvent. It has low toxicity, but limonene that has oxidised in air can cause skin allergy in some people, so cosmetic labels must name it above set levels.
Key facts
- Chemical class
- Monoterpene (a cyclic hydrocarbon), C10H16, with two mirror-image forms, d- and l-limonene
- Smell
- d-Limonene smells of orange; l-limonene has a piney, turpentine-like note
- Where it occurs
- Citrus peel oils above all, and also hemp and cannabis, mint, juniper, rosemary and fennel
- Labelling
- Must be named in a cosmetic's ingredient list above 0.001% in leave-on and 0.01% in rinse-off products (UK Cosmetics Regulation, Annex III, as of October 2026)
- Legal status
- Not a controlled substance; it does not cause a high
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What is limonene?
Limonene is one of the terpenes, the aromatic compounds plants use to attract pollinators and keep insects away. It is a colourless liquid that mixes with oils and alcohol but hardly with water. It is a major constituent of orange, lemon, mandarin, lime and grapefruit oils (Sun, 2007).
What are citrus terpenes?
"Citrus terpenes" is the everyday name for the aromatic compounds in citrus peel. Limonene makes up most of them. Smaller amounts of other terpenes, such as linalool, add to the scent (Wang et al., 2023). The oil is pressed or distilled from the peel, which is why products sold as "citrus terpenes" or "citrus solvent" are mainly limonene.
The same compounds occur outside citrus. In cannabis and hemp, limonene is one of the terpenes that can give a variety a lemon or orange note.
What is the chemical structure of limonene?
Limonene is a monoterpene: two isoprene units joined into one ring, giving the formula C10H16 (PubChem). It has one chiral centre, so it exists in two mirror-image forms:
- d-Limonene, or (R)-(+)-limonene, is the form in citrus peel. It smells of orange.
- l-Limonene, or (S)-(−)-limonene, is less common and occurs in mint and conifers. It smells more of pine and turpentine.
A 2024 study found that the (+) form made up more than 97% of the limonene from fragranced consumer products, while conifers released varying ratios (Gu et al., 2024). When a label says only "limonene", it usually means d-limonene.
| d-Limonene | l-Limonene | |
|---|---|---|
| Other names | (R)-(+)-limonene | (S)-(−)-limonene |
| Smell | Orange, citrus | Pine, turpentine |
| Main sources | Orange, lemon and other citrus peel | Mint, conifers |
| In consumer products | The dominant form | Rarely used |
Is limonene in cannabis?
Yes. Limonene is one of the terpenes in cannabis and hemp resin. A citrus smell does not prove that a variety is high in limonene, and amounts change with genetics, growing conditions and processing after harvest. Only a laboratory analysis shows how much a batch contains.
Limonene is one of the terpenes discussed in connection with the entourage effect. In a small controlled trial with 20 healthy adults, inhaled d-limonene taken with THC reduced the anxiety that THC caused on its own. Limonene alone had no measurable effects compared with placebo (Spindle et al., 2024). This is one early study, not proof of a wider effect.
What is limonene used for?
- Fragrance: perfumes, soaps, shampoos, lotions and air fresheners.
- Solvent: degreasers, furniture polish and other cleaners, because it dissolves oils and grease.
- Flavouring: it is listed in the United States as generally recognised as safe for use as a flavouring.
Limonene oil is obtained from citrus peel by cold pressing or steam distillation, or with solvents. It can also be made by chemical synthesis or by engineered microbes.
Is limonene safe?
d-Limonene has low toxicity. In humans, single and repeated doses for up to one year showed low toxicity, and the kidney tumours once seen in male rats arise through a mechanism that does not apply to people (Sun, 2007).
On skin, the main issue is oxidation. Limonene exposed to air forms products that can cause contact allergy. In a Swedish clinic that patch-tested 5,773 people with dermatitis, 5.1% reacted to oxidised limonene (Sukakul et al., 2022). That is why the UK Cosmetics Regulation requires limonene to be named in the ingredient list above 0.001% in leave-on and 0.01% in rinse-off products.
Concentrated limonene is not for pets. In cats, an insecticidal dip with d-limonene caused drooling, unsteadiness and tremors at five and fifteen times the recommended strength (Hooser et al., 1986).
From our production
We keep the hemp's natural terpenes in our oils rather than stripping them out. Many people underestimate terpenes and assume only the cannabinoids matter.
— Robin Roy Krigslund-Hansen, co-founder and CEO
Frequently asked questions
What is limonene?
Limonene is a terpene with a fresh citrus smell. It is the main aromatic compound in citrus peel and also occurs in hemp, cannabis, mint and juniper.
Are citrus terpenes the same as limonene?
Mostly. "Citrus terpenes" are the aromatic compounds in citrus peel, and limonene makes up most of them. Products sold as citrus terpenes or citrus solvent are mainly limonene.
What does limonene smell like?
d-Limonene, the common form, smells like freshly peeled orange. The rarer l-limonene smells more of pine and turpentine.
Is limonene found in all cannabis strains?
No. Levels vary with genetics, growing conditions and processing, and a citrus smell is not proof of a high level. Only a laboratory analysis of the batch shows the content.
Is limonene safe on skin?
Limonene has low toxicity, but once it oxidises in air it can cause allergic skin reactions in sensitive people. That is why cosmetics must name it on the label above set levels.
Can limonene degrade over time?
Yes. Light, heat and air break limonene down, and the oxidation products are what can irritate sensitive skin. Keep products containing it closed and away from heat.
Related guides
This article is for information only and does not describe any product in our shop. Formula Swiss CBD oils are cosmetic products for use on the skin. They are not medicines. See our full disclaimer.
Last reviewed:
Sources
- National Library of Medicine. Limonene, compound summary. PubChem.
- Sun J. D-limonene: safety and clinical applications. Altern Med Rev 2007;12(3):259–264.
- Gu S, Luo W, Charmchi A, et al. Limonene enantiomeric ratios from anthropogenic and biogenic emission sources. Environ Sci Technol Lett 2024. doi:10.1021/acs.estlett.3c00794
- Spindle TR, Zamarripa CA, Russo E, et al. Vaporized D-limonene selectively mitigates the acute anxiogenic effects of Δ9-tetrahydrocannabinol in healthy adults who intermittently use cannabis. Drug Alcohol Depend 2024. doi:10.1016/j.drugalcdep.2024.111267
- Sukakul T, Bruze M, Mowitz M, et al. Contact allergy to oxidized linalool and oxidized limonene: patch testing in consecutive patients with dermatitis. Contact Dermatitis 2022. doi:10.1111/cod.13980
- Wang Q, et al. Promoter characterization of a citrus linalool synthase gene mediating interspecific variation in resistance to a bacterial pathogen. BMC Plant Biol 2023. doi:10.1186/s12870-023-04413-6
- Hooser SB, Beasley VR, Everitt JI. Effects of an insecticidal dip containing d-limonene in the cat. J Am Vet Med Assoc 1986. doi:10.2460/javma.1986.189.08.905
- Regulation (EC) No 1223/2009 on cosmetic products, Annex III, entry 88 (limonene), as it applies in Great Britain. legislation.gov.uk.
