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Ingredient

Citronellol

Contributes to the fragrance profile of the formulation.

At a glance

Function
Fragrance
Origin
Plant-derived or synthetic
Product areas
Hair care, Hair styling, Straightening products

What it is

Citronellol carries the rosy-citrus note of many fragrance mixtures and appears in six products in this lexicon. Like linalool and limonene it is a terpene and shares their decisive property: it oxidises in air.

For this substance it is particularly well documented how quickly that happens. In one study the proportion of hydroperoxides in air-exposed citronellol rose to around nine per cent after ten weeks and to 21 per cent after 26 weeks. Other oxidation products formed only in small amounts — and the hydroperoxides are at the same time the only ones identified as sensitisers.

Assessment

Result
Increased attention
Confidence
medium
Evidence
C — limited evidence
Applies to
Cosmetics, external use on hair and scalp; rinse-off care, styling products and one straightening product; the assessment refers to the substance including its oxidation products; concentration and degree of oxidation not documented

Why

  • Why the classification reads “increased attention”: in a study of 658 eczema patients, purified and oxidised citronellol were tested side by side. The difference between the two forms is the actual finding — not the absolute frequency.
  • The figures on oxidation are more tangible here than for the related substances. After ten weeks of air contact around nine per cent hydroperoxides, after 26 weeks 21 per cent: that is the clearest evidence of why storage and standing time are no side issue with fragrances.
  • Short field corrected: until 10.09.2026 the function read “fragrance or declarable fragrance allergen”. The second part is a legal statement, and this lexicon does not quote regulations second-hand. The function now reads simply “fragrance” in all four languages, as with the three other records in this block. That individual fragrance components appear separately in the lists is described in the text on parfum.
  • Structure makes the difference. Citronellol and the closely related geraniol differ by only one double bond — and therefore oxidise differently. With citronellol the hydroperoxides alone are the sensitisers; with geraniol aldehydes are added. Similar-looking names therefore do not mean the same finding.
  • The evidence base is thinner than for linalool and limonene. That is why the evidence level here is C and not B. The mechanism is the same and well documented; the frequency in the population is less so.

When the assessment differs

  • Known allergy to oxidised citronellol: then the product is unsuitable. What is tested is the oxidised form.
  • Existing eczema or atopic dermatitis: a lower threshold for sensitisation.
  • Old or long-opened products: with this substance the connection with standing time is particularly well documented.
  • Occupational contact in the salon: daily contact with many fragranced products on the hands.
  • Products that stay on hair and skin: citronellol also appears here in styling products and one straightening product.

Open questions

  • Concentration in the specific product: not available.
  • Degree of oxidation in the specific product: not determinable.
  • Frequency of an allergy to oxidised citronellol in the general population: not quantified here. The available figures come from a pre-selected group at dermatology clinics.
  • Origin of the citronellol used: the short field says plant-derived or synthetic; which route was chosen is not documented.
  • Regulatory status and the rules on individual naming: not checked; they are not quoted second-hand.

Sources for this assessment

Applies to: Fragrance materials

Further substances from the same group for which a long-form assessment already exists.

Assessment last reviewed:

Recorded in the following products

This list documents the products in which the ingredient was declared at the time of recording. It is not a statement about those products and not a recommendation. Manufacturers change formulations; the ingredient list on the current packaging is always authoritative.

  • Wella Nutricurls Micellar Curls Shampoo
  • Schwarzkopf SESSION LABEL The Definer
  • Schwarzkopf SESSION LABEL The Coat
  • Matrix Controller Gel
  • Matrix Over Achiever 3-in-1
  • Schwarzkopf Strait Styling

Sources documenting its occurrence

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