Limonene

What is limonene and what is it used for?

Limonene is a terpene and the main component of the essential oils in citrus peel. It is mostly obtained from orange peel left over from juice production. It gives a fresh, clean citrus scent, and it also has the ability to dissolve oils and sticky residues.

Thanks to these two properties, it is used both as a fragrance ingredient in fragrance blends and as a solvent in naturally derived cleaners. It is also present in food as a flavouring. Because in cosmetics and cleaning products it is mostly plant-derived, you will often come across it in products labelled “natural” or “botanical”; in these products the level of limonene may even be higher than in products with synthetic fragrances.

Which products contain it?

• Perfumes, eau de cologne and deodorants
• Citrus-scented shampoos, shower gels and lotions
• “Orange oil” surface cleaners and degreasers
• Washing-up liquids, fabric softeners and air fresheners

Is it harmful? The scientific assessment

Pure, fresh limonene is a weak allergen for the skin. When it comes into contact with air it oxidises, and the hydroperoxides that form are strong sensitisers. In patch tests with oxidised limonene in dermatology clinics, positive reactions have been found in a proportion of patients with eczema. This shows that how long a product has been open and how it is stored matter.

Reactions linked to limonene are uncommon in the general population. Pure limonene can irritate the eyes and skin, which is why wearing gloves with concentrated cleaners is important. It is also classified as harmful to aquatic life, which calls for mindful use of cleaning products.

Limonene is not classified as carcinogenic to humans. It may be used in cosmetics in the EU; above a certain threshold, it must be listed by name in the ingredient list.

Who should be careful?

• People with a fragrance allergy or a limonene sensitivity shown in a patch test: They should choose fragrance-free products and also check for citrus essential oils.
• People with hand eczema: Contact with orange oil degreasers without gloves can irritate the skin.
• People with sensitive skin: For leave-on, strongly scented products, fragrance-free options carry less risk.

What to do when you see it on a label

If you don't have an allergy, there is no reason not to use a product containing limonene. Storing products with the lid closed in a cool place and not using old products reduces the risk of oxidation. If you have a fragrance allergy, look on the label for other allergens that must be declared, such as linalool, as well as limonene; a “natural” or “organic” claim does not mean these substances are absent.