Geraniol

What it is

Geraniol carries the rosy note of many fragrance mixtures and appears in six products in this lexicon. It belongs to the same substance group as linalool, limonene and citronellol and shares their basic problem: it ages in air. With this substance, however, that happens by a different route.

Linalool and limonene mainly form hydroperoxides as they age. Geraniol forms, alongside those and predominantly, two aldehydes — geranial and neral. Taken together these two are nothing other than citral, which has its own record in this same block. Aged geraniol therefore essentially becomes citral. The two entries in an ingredient list are not independent of each other.

Why

• Why the classification reads “increased attention”: in a Swedish study pure and aged geraniol were tested side by side in around 2,200 consecutive eczema patients each. Pure geraniol gave 0.13 per cent positive reactions, aged geraniol 0.55 per cent — a good four times as many. The substance itself is a weak allergen, its ageing product is not.
• The route differs from linalool and limonene, and that is the actual finding of this record. As it ages, geraniol forms not only hydroperoxides but predominantly the aldehydes geranial and neral. Eight of eleven people who reacted to aged geraniol also reacted, in the same study, to citral or its components.
• There is also a property that sets this substance apart from the three fragrances of the eleventh block: geraniol is activated not only in air but by the skin itself. Skin enzymes convert it into the same aldehydes. In practice this means that a fresh product does not give the same all-clear here as with linalool — part of the conversion only happens after application.
• Origin corrected: until 11.09.2026 the short field named geranium. Geraniol does occur in geranium oil, but mainly in rose, palmarosa and citronella oil, and for cosmetics it is equally produced on an industrial scale. Which route was chosen is not stated in the ingredient list. The short field now reads “plant-derived or synthetic” in all four languages — the same correction as with linalool and lavender.
• A practical rule follows for advice at the chair, one that applies to all terpenes in this lexicon and is clearest here: the age and storage of a product say more about tolerability than the ingredient list. With geraniol there is the added point that the skin itself does part of the work.

When the assessment differs

• Known allergy to aged geraniol: then the product is unsuitable. What is tested is the aged form; the pure substance often does not reveal the allergy.
• Known citral allergy: anyone reacting to citral belongs to the group with a high risk of co-reaction — chemically the two are the same pair of molecules in two states of ageing.
• Existing eczema or atopic dermatitis: a lower threshold for sensitisation.
• Old or long-opened products: the longer air reaches the formulation, the more aldehydes and hydroperoxides can form.
• Spray products: in this lexicon the substance also appears in a hairspray. Inhalation is a route of its own and is not assessed here.

Open questions

• Concentration in the specific product: not available.
• Degree of oxidation in the specific product: not determinable and not readable from the ingredient list.
• Share of conversion by the skin compared with ageing in air: described in the literature as two separate routes; their respective contribution under conditions of use is not quantified here.
• Origin of the geraniol used: not documented.
• Regulatory status and the rules on individual naming: not checked; they are not quoted second-hand.

Sources for this assessment

• Hagvall L., Karlberg A.-T., Bråred Christensson J.: Contact allergy to air-exposed geraniol — clinical observations and report of 14 cases. Contact Dermatitis, Band 67, Heft 1, 2012, Seiten 20–27. Reines und gealtertes Geraniol an jeweils rund 2.200 aufeinanderfolgenden Personen getestet. Begutachtete Fachzeitschrift, abgerufen am 11.09.2026.
• Hagvall L. u. a.: Fragrance Compound Geraniol Forms Contact Allergens on Air Exposure — Identification and Quantification of Oxidation Products and Effect on Skin Sensitization. Chemical Research in Toxicology, 2007. Beschreibt, dass Geraniol einem anderen Oxidationsmuster folgt als Linalool und Limonene und dabei überwiegend die Aldehyde Geranial und Neral bildet. Begutachtete Fachzeitschrift, abgerufen am 11.09.2026.

Related substances

Applies to: Fragrance materials

• Alpha-Isomethyl Ionone — Fragrance
• Benzyl Salicylate — Fragrance
• Citral — Fragrance
• Citronellol — Fragrance

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