At a glance
| Chemical family | A monoterpene aldehyde (a mixture of the isomers geranial and neral); the dominant constituent of lemongrass and lemon myrtle oils |
| CAS number | 5392-40-5 |
| Classification | Not IARC-classified (absence of evaluation, not a safety finding). The second-largest allergen in Fragrance Mix II (16.1% of FM II-positives); an EU-declared fragrance allergen |
| Where you encounter it | Lemon-scented detergents, household cleaners, soaps and personal care; naturally in lemongrass, lemon myrtle and citrus oils; a food flavouring |
| Sleep micro-environment relevance | A ubiquitous laundry and cleaning-product fragrance, so it sits on bedding at the skin and breathing zone; as a terpene it also oxidizes over time into stronger sensitizers |
| Activated carbon capture | Partly — as a semi-volatile fragrance it can be captured from air, but fragrance-free laundry products are the cleaner lever |
What it is
Citral is a monoterpene aldehyde — really a mixture of two isomers, geranial and neral — and it is the compound that smells of lemon. It dominates lemongrass and lemon myrtle oils and is used enormously widely as a fragrance in detergents, household cleaners, soaps and personal-care products, and as a flavouring. Peer-reviewed — Krautheim et al. 2010
Citral is not IARC-classified; it does not appear in the IARC list of classified agents. Inferred — citral does not appear in the IARC list of classified agents; that is an absence of evaluation, not a finding of safety So this is not a cancer page. It is an allergy page, and citral has a strong claim to one: within the Fragrance Mix II panel it is the second-biggest allergen, well ahead of most of the compounds it is mixed with.
How it relates to the bedroom
The fragrance that survives the wash
Citral is one of the defining notes of "fresh" and "lemon" cleaning and laundry products, and laundry fragrance is engineered to persist on fabric. So it sits on washed bedding at the skin and breathing zone, and it is also in the air from cleaning products used in the room. Inferred — from citral's documented use as a detergent and cleaner fragrance and the designed persistence of laundry scent; citral specifically has not been measured on laundered bedding
The second-biggest allergen in Fragrance Mix II
Citral is one of the six constituents of Fragrance Mix II, the mix developed to catch fragrance allergies that Fragrance Mix I misses. In an IVDK series of 35,633 patients, 4.9% reacted to Fragrance Mix II. Peer-reviewed — Krautheim et al. 2010
Within that mix, citral is a heavyweight. Of 367 FM II-positive patients given a full breakdown test, 16.1% reacted to citral — second only to hydroxyisohexyl 3-cyclohexene carboxaldehyde at 47.7%, and far ahead of coumarin (2.7%) and citronellol (2.5%). Peer-reviewed — Krautheim et al. 2010 If you are reacting to a lemon-scented product, citral is a reasonable first suspect.
A terpene, so it gets worse with age
Citral is a terpene, and terpenes share an inconvenient habit: they autoxidize on contact with air. The pattern is best documented for linalool, where the fresh molecule showed no sensitizing potential but its air-exposed hydroperoxides were clearly positive sensitizers. Peer-reviewed — Sköld et al. 2004 The same air-oxidation chemistry applies to citral as an unsaturated terpene, so an aged, air-exposed product is a more potent sensitizer than a fresh one. Inferred — the autoxidation-to-hydroperoxide mechanism is directly demonstrated for linalool and limonene; extending it to citral follows from the shared terpene chemistry, but citral-specific oxidation data are not cited here
Citral is an EU-declared fragrance allergen and must be named on cosmetic labels above threshold (0.001% leave-on, 0.01% rinse-off), with compliance from 31 July 2026. Regulatory — EU 2023/1545
What the research says
- Not IARC-classified. Citral does not appear in the IARC list; an absence of evaluation, not a safety finding. Inferred
- The second-biggest Fragrance Mix II allergen. 16.1% of FM II-positive patients reacted to citral, vs 47.7% for the top allergen and 2.7% for coumarin. Peer-reviewed — Krautheim et al. 2010
- FM II positivity is 4.9%. Of 35,633 patch-tested patients. Peer-reviewed — Krautheim et al. 2010
- A terpene, so it oxidizes. Air exposure converts terpenes into stronger sensitizers; aged product is more allergenic. Inferred — from the demonstrated linalool/limonene autoxidation mechanism
- EU-declared allergen. Must be named on cosmetic labels above threshold. Regulatory — EU 2023/1545
What helps reduce it
Use fragrance-free detergent and lemon-free cleaners on bedding. Citral is the "fresh lemon" note, so this is where it actually reaches you. Inferred
If you are fragrance-allergic, note that Fragrance Mix I can miss it. Citral sits in Fragrance Mix II, which exists precisely to catch what FM I misses. Peer-reviewed — Krautheim et al. 2010
Prefer fresh products over long-aged scented ones. Terpene oxidation raises allergenic potency with air exposure over time. Inferred
What does NOT help
- Treating it as a cancer risk. Citral is not IARC-classified; the documented hazard is contact allergy. Inferred
- Assuming "natural lemon oil" is safer. Lemongrass and lemon myrtle oils are the richest natural sources of citral; natural origin does not reduce the sensitization. Inferred
Open research questions
- How much citral actually persists on laundered bedding from detergent fragrance — not measured. Speculation
- Whether citral-specific autoxidation products have been characterized as thoroughly as those of linalool and limonene, and how much they raise its potency. Speculation
Citations
- Krautheim A, Uter W, Frosch P, Schnuch A, Geier J (2010). Patch testing with fragrance mix II: results of the IVDK 2005–2008. Contact Dermatitis 63(5):262–269. Of 35,633 patients patch-tested with Fragrance Mix II, 1,742 (4.9%) reacted positively. In 367 FM II-positive patients given a full breakdown, 16.1% reacted to citral — second only to hydroxyisohexyl 3-cyclohexene carboxaldehyde (47.7%), and well ahead of coumarin (2.7%) and citronellol (2.5%). PMID 20946454. doi.org/10.1111/j.1600-0536.2010.01753.x Peer-reviewed
- Sköld M, Börje A, Harambasic E, Karlberg A-T (2004). Contact allergens formed on air exposure of linalool. Chemical Research in Toxicology 17(12):1697–1705. Cited here for the terpene autoxidation mechanism: the fresh molecule showed no sensitizing potential, while its air-exposed hydroperoxides were clearly positive sensitizers. PMID 15606147. doi.org/10.1021/tx049831z Peer-reviewed
- Commission Regulation (EU) 2023/1545 amending Regulation (EC) No 1223/2009 as regards labelling of fragrance allergens (Annex III). Citral must be declared on cosmetic labels above 0.001% (leave-on) / 0.01% (rinse-off); compliance from 31 July 2026. EUR-Lex Regulatory
Frequently asked questions
What is citral?
Citral is a monoterpene aldehyde (a mixture of the isomers geranial and neral) and the compound that smells of lemon. It is the dominant constituent of lemongrass and lemon myrtle oils and is very widely used as a fragrance in detergents, household cleaners, soaps and personal care, and as a flavouring. In the bedroom it reaches you as fragrance that persists on laundered bedding.
Is citral a carcinogen?
Citral does not appear in the IARC list of classified agents, so it has no IARC carcinogenicity classification. That is an absence of evaluation rather than a finding of safety. Its documented hazard is skin sensitization, where it is a substantial contributor — the second-largest allergen in the Fragrance Mix II screening panel.
How allergenic is it?
Substantially. Citral is one of the six constituents of Fragrance Mix II. In an IVDK series of 35,633 patients, 4.9% reacted to Fragrance Mix II; of 367 FM II-positive patients given a full breakdown test, 16.1% reacted to citral. That makes it the second-largest contributor in the mix, behind hydroxyisohexyl 3-cyclohexene carboxaldehyde (47.7%) and far ahead of coumarin (2.7%).
Should I be worried about it?
If you have no fragrance allergy, citral in a lemon-scented cleaner is not a cancer concern. If you have fragrance-allergic dermatitis, citral is one of the more likely culprits, and it is a terpene — so like limonene and linalool it oxidizes in air into stronger sensitizers as a product ages. Fragrance-free bedding laundry is the direct fix, and the EU requires citral to be declared on cosmetic labels.
Related compounds
Embr is a sleep environment company researching and addressing the chemistry of the bedroom. Research and product development in progress.
Last reviewed 2026-07-14. If you find a factual error, contact us.