At a glance
| Chemical family | A synthetic saturated hydroxy-aldehyde (7-hydroxy-3,7-dimethyloctanal); the lily-of-the-valley (muguet) note. Being saturated, it does not carry the terpene autoxidation story |
| CAS number | 107-75-5 |
| Classification | Not IARC-classified (absence of evaluation, not a safety finding). A classic contact sensitizer and a constituent of Fragrance Mix I (7.7% panel positivity); an EU-declared fragrance allergen whose use is restricted |
| Where you encounter it | Perfumes, detergents, soaps, fabric softeners and personal-care products; a synthetic material, not a natural essential-oil constituent |
| Sleep micro-environment relevance | Fragrance that survives laundering and sits against the skin all night; for the fragrance-allergic, a pillowcase is eight hours of warm, occluded contact with a well-established sensitizer |
| Activated carbon capture | Not the main lever — the exposure that matters is skin contact with treated fabric, so fragrance-free laundry is the direct fix |
What it is
Hydroxycitronellal is a synthetic hydroxy-aldehyde with a soft lily-of-the-valley, or muguet, scent. It is one of the classic materials of perfumery and is used widely in detergents, soaps, fabric softeners and personal-care products. Peer-reviewed — Buckley et al. 2006
Hydroxycitronellal is not IARC-classified; it does not appear in the IARC list of classified agents. Inferred — hydroxycitronellal 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 hydroxycitronellal has one of the longest track records of any fragrance sensitizer: it is one of the eight compounds in Fragrance Mix I, the original screening panel, and it is there because it reliably sensitizes skin.
How it relates to the bedroom
The fragrance that survives the wash
Hydroxycitronellal's bedroom route is ordinary fragrance. It is used in detergents, soaps and fabric softeners, and laundry scent is engineered to persist on fabric, so it remains on washed bedding pressed against skin. Inferred — from hydroxycitronellal's documented use as a detergent and personal-care fragrance and the designed persistence of laundry scent; it has not specifically been measured on laundered bedding For most sleepers this is unremarkable. For someone sensitized to it, it is a nightly, warm, occluded dose to the face and neck.
A classic Fragrance Mix I sensitizer
Hydroxycitronellal is one of the eight constituents of Fragrance Mix I, the original standard screening mix for fragrance allergy. In a series of 23,660 patients patch-tested to the European standard series, 7.7% reacted to Fragrance Mix I. Peer-reviewed — Buckley et al. 2006
Its membership of that panel is the point. Fragrance Mix I was assembled from the materials that most reliably turned up as culprits in fragrance-allergic dermatitis, and hydroxycitronellal has been on that list for decades. Its concentration in cosmetics is restricted for exactly this reason, rather than for any cancer concern. Regulatory — EU 2023/1545
One story that does NOT apply to it
A useful negative. Much of this fragrance cluster — linalool, limonene, geraniol, citral — shares an autoxidation problem: they are unsaturated terpenes that react with air to form hydroperoxides far more sensitizing than the parent molecule. Peer-reviewed — Sköld et al. 2004 Hydroxycitronellal is saturated, so that particular mechanism does not apply to it in the same way, and an aged bottle is not the specific worry here. Inferred — from hydroxycitronellal's saturated structure, which lacks the carbon-carbon double bond that drives terpene autoxidation; this is a structural argument, not a measured comparison Its sensitizing potential is intrinsic rather than something it acquires on the shelf.
What the research says
- Not IARC-classified. It does not appear in the IARC list; an absence of evaluation, not a safety finding. Inferred
- A Fragrance Mix I constituent. 7.7% of 23,660 patch-tested patients reacted to Fragrance Mix I. Peer-reviewed — Buckley et al. 2006
- A classic, long-recognised sensitizer. It is in the original screening panel because it reliably causes fragrance-allergic dermatitis. Inferred — from its inclusion in FM I, which was assembled from the most reliable culprits
- Restricted, not just declared. Its concentration in cosmetics is capped because of sensitization. Regulatory — EU 2023/1545
- Saturated, so no autoxidation story. Unlike the terpenes, it does not become a stronger allergen as a product ages. Inferred — structural argument from its saturated backbone
What helps reduce it
Use fragrance-free detergent on bedding. For a sensitized sleeper this is the single highest-yield change, because it removes a reliable allergen from eight hours of occluded skin contact. Inferred
If you suspect fragrance allergy, ask for the Fragrance Mix I breakdown. Hydroxycitronellal is one of its eight constituents. Peer-reviewed — Buckley et al. 2006
Read the EU allergen declarations. It must be named on the label above threshold. Regulatory — EU 2023/1545
What does NOT help
- Treating it as a cancer risk. It is not IARC-classified; the documented hazard is contact allergy. Inferred
- Buying fresher product to avoid oxidation. That lever works for the unsaturated terpenes, not for this saturated molecule. Inferred — structural argument
Open research questions
- How much hydroxycitronellal actually persists on laundered bedding from detergent fragrance — not measured. Speculation
- Whether the concentration restrictions have measurably reduced sensitization rates over time. Speculation
Citations
- Buckley DA, Basketter DA, Smith Pease CK, Rycroft RJG, White IR, McFadden JP (2006). Simultaneous sensitivity to fragrances. British Journal of Dermatology 154(5):885–888. Of 23,660 patients patch-tested to the European standard series, 1,811 (7.7%) reacted to Fragrance Mix I; hydroxycitronellal is one of the eight constituents of that mix. PMID 16634891. doi.org/10.1111/j.1365-2133.2006.07170.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 only for the contrast: the terpene autoxidation-to-hydroperoxide mechanism, which does not apply to saturated hydroxycitronellal. 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). Hydroxycitronellal 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 hydroxycitronellal?
Hydroxycitronellal is a synthetic hydroxy-aldehyde (7-hydroxy-3,7-dimethyloctanal) with a soft lily-of-the-valley, or muguet, scent. It is one of the classic fragrance materials, used in perfumes, detergents, soaps and personal-care products. In the bedroom it reaches you as fragrance that persists on laundered bedding.
Is hydroxycitronellal a carcinogen?
It 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, and on that count it has a long and well-established record.
How allergenic is it?
It is one of the eight constituents of Fragrance Mix I, the original standard screening mix for fragrance allergy; 7.7% of 23,660 patients patch-tested to the European standard series reacted to that mix. Hydroxycitronellal earned its place in that panel by being a reliable sensitizer, and its concentration in cosmetics is restricted for the same reason.
Should I be worried about it?
If you have no fragrance allergy, no — it is not a carcinogen. If you have fragrance-allergic dermatitis, hydroxycitronellal is a genuine and long-recognised culprit, which is why it sits in the standard screening panel and why its use is capped. Unlike the terpenes, it is a saturated molecule, so the "aged product oxidizes into a stronger allergen" story does not apply to it in the same way. Fragrance-free bedding laundry is the direct fix.
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.