Geraniol

What it is

Geraniol is the main rose-like note in geranium, palmarosa, citronella and rose oils, and it is also produced synthetically. It is a component of the classic fragrance mix I patch-test panel, so its allergenic potential has been studied for decades. In cosmetics it appears both as an added fragrance material and as a natural constituent of many floral essential oils.

What it does well

• Provides a rose or floral note used across the industry

  Geraniol is one of the workhorse floral aroma chemicals. This is a sensory benefit; there is no established skincare benefit from geraniol itself.

  Strong evidence

• Has documented insect-repellent activity

  Geraniol is registered as an insect repellent in some jurisdictions and is used in citronella-type products. This is not relevant to face masks and is included only for context.

  Moderate evidence

Worth knowing

• Oxidised geraniol is markedly more allergenic than the fresh material

  In a Swedish multicentre study of 1476 consecutively patch-tested patients, pure geraniol at 6% gave positive reactions in 1%, oxidised geraniol at 6% in 3%, and oxidised geraniol at 11% in 8%. Air exposure clearly increases its sensitising potency.

  Matters most toPeople with eczema or a known fragrance allergy.

• The skin itself can activate geraniol into an allergen

  Laboratory work shows cytochrome P450 enzymes in skin can convert geraniol into geranial and other reactive products that behave as potent contact allergens. This is one reason a molecule that looks benign on paper causes real-world allergy.

  Matters most toPeople investigating an unexplained fragrance reaction.

• Cross-reacts with citral

  Because geraniol oxidises to geranial, people allergic to geraniol often react to citral as well, and vice versa.

  Matters most toPeople with a confirmed allergy to either substance.

Where the EU stands

Sources (3)

Every link goes to the original: a journal, a PubMed record or an EU document.

1. [1]
   Contact allergy to oxidized geraniol among Swedish dermatitis patients - A multicentre study by the Swedish Contact Dermatitis Research Group

   Contact Dermatitis · 2018 · doi:10.1111/cod.13047

   Among 1476 consecutively patch-tested patients, positive reactions rose from 1% with pure geraniol to 8% with oxidised geraniol at 11%, showing air exposure substantially increases its allergenic potency.

2. [2]
   Cytochrome P450-mediated activation of the fragrance compound geraniol forms potent contact allergens

   Toxicology and Applied Pharmacology · 2008 · doi:10.1016/j.taap.2008.08.014

   Skin enzymes can metabolise geraniol into geranial and other reactive species that act as potent contact allergens, explaining why a weak sensitiser on paper causes real clinical allergy.

3. [3]
   Contact allergy to air-exposed geraniol: clinical observations and report of 14 cases

   Contact Dermatitis · 2012 · doi:10.1111/j.1600-0536.2012.02079.x

   A case series confirming that patients react to air-exposed geraniol while often testing negative to the fresh material, supporting the use of oxidised geraniol in patch-test series.