Ingredient guide

Limonene: The Citrus Scent That's a Declared Allergen

Limonene gives products a fresh citrus note and is one of the 26 EU-declared fragrance allergens. Here's what it is, who reacts, and where to spot it.

What it is

Limonene is a naturally occurring scent compound found in citrus peel oils. It gives products a fresh, zesty note and is used very widely, including in many “natural” ranges because it comes from plants.

Why it is listed separately

Limonene is one of the 26 fragrance allergens that UK and EU rules require to be named individually on the label when present above a set level. That is why you will sometimes see it spelled out at the end of an ingredient list even when the product just says “fragrance” higher up.

Who tends to react

Once oxidised (after a product has been open a while), limonene becomes more likely to trigger contact allergy. People with fragrance sensitivity, eczema or a history of contact dermatitis are most affected.

Where it hides

Citrus-scented skincare, shampoos, shower gels, botanical ranges and household cleaners. Look for Limonene or D-Limonene, usually near the end of the ingredient list.

Check products against your list

To check a product, SkinSAFE lets you filter a product catalogue to screen out limonene and other allergens, and a free browser extension like Clearya flags ingredients of concern automatically as you shop online. These rate a product on general criteria rather than against your own list.

Once you know what you are screening for, a personal-list app like ClearaScan lets you save limonene once and scan any product to flag only your triggers. It also keeps a Reaction Journal for flare-ups, a shared Care Circle so family or carers can scan for you, and a Trusted Products list for items you have cleared, and it is currently in early access. (Disclosure: our editor co-founded ClearaScan, and we are not paid to mention the others.)

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A note on this content. The Sensitive Skin Lab publishes general educational information, not medical advice. If you suspect you have an allergy or sensitivity, consult a qualified dermatologist or allergist. Product formulations and labels change without notice, so always check the ingredients on the product itself.