Limonene
d-Limonene
What it is
A citrus-peel terpene (CAS 5989-27-5), one of the most widely used scent chemicals on earth.
In this product: Fresh citrus fragrance note; also a solvent.
Dose & route, what actually matters
The molecule itself is benign. Its oxidation products (hydroperoxides), formed once the can is opened and on the skin surface, are the actual sensitizers. Matters most for people with reactive skin.
EUROPEAN UNION
Named-disclosure fragrance allergen (Annex III) since 2003; reaffirmed 2023.
UNITED STATES
No individual disclosure required.
The evidence
Patch testing 2,273 patients across four EU clinics with oxidized R-(+)-limonene found 3.8–6.5% positive reactions, supporting its classification as a skin sensitizer.
human · 2002 · source
Roughly 10% of people investigated for contact dermatitis were allergic to the hydroperoxides of limonene and linalool.
review · 2018 · source
California Prop 65: Not listed. (Do not confuse with beta-myrcene, a different terpene that is listed.)
How to avoid it
Fragrance-free products avoid it. If you tolerate citrus scents on skin, it’s likely fine for you.
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.