Isoeugenol
2-Methoxy-4-(1-propenyl)phenol
What it is
A phenolic fragrance compound found in ylang-ylang and nutmeg oils, a structural cousin of eugenol. The most allergenic of the common clove-floral notes, and the only one the EU put a hard cap on.
In this product: Fragrance. A warm spicy-floral clove note.
Dose & route, what actually matters
Allergic contact dermatitis from leave-on skin exposure in sensitised people. The EU capped it at 200 ppm precisely because sensitisation occurred at higher leave-on levels.
EUROPEAN UNION
Annex III, entry 73. Capped at 0.02% in non-oral cosmetics and required on the label above the standard allergen thresholds, per Commission Regulation (EU) 2023/1545. The fragrance industry's own IFRA standard restricted it to 200 ppm back in 1998.
UNITED STATES
No federal cap. California's 2020 Right-to-Know Act requires disclosure at EU thresholds. Otherwise inside “Fragrance.”
The evidence
Isoeugenol was the most common individual allergen among fragrance-mix-positive patients, positive in 57.9% (91 of 157) tested.
human · 2000 · source
EU Annex III entry 73 caps isoeugenol at 0.02% in non-oral cosmetics and requires label declaration above the standard allergen thresholds.
regulatory · 2023 · source
California Prop 65: Not listed.
How to avoid it
Look for “isoeugenol” on EU labels. Compliant products stay under the cap, but already-sensitised skin can react to low levels, so fragrance-free is the safe route if you patch-test positive.
Where it hides
Editorial analysis of publicly available regulatory and peer-reviewed sources. Not medical advice. We name our evidence and link it, including when an ingredient is fine.