Definition and Uses in Cosmetics: Limonene is a naturally occurring fragrance compound found in the rind of citrus fruits, but it can also be produced synthetically. It is a colorless liquid with a light, fresh, and sweet citrus odor used to make fragrances and flavors. Limonene functions as a fragrance ingredient and solvent in cosmetics and personal care products. It is used in the formulation of aftershave lotions, bath products, bubble baths, cleansing products, eye shadows, hair products, lipsticks, mascara, moisturizers, perfumes and colognes, shampoos, skin care products, and suntan products.

Other Names: Limonene is also known as dipentene, and it contains one or more of the following stereoisomers: d-limonene, l-limonene, or (racemic) dl-limonene​.

Skin Sensitivities: Limonene can potentially cause skin sensitization, which is why its use is restricted in fragrances. The International Fragrance Association (IFRA) has established a standard that restricts the use of Limonene due to this potential for sensitization​.

Risks: While Limonene is generally recognized as safe (GRAS) by the FDA and other organizations for use as a flavoring agent, it is included on the list of "allergenic" substances in Europe. The European Cosmetics Directive requires manufacturers of cosmetics and personal care products to indicate the presence of Limonene in the list of ingredients when its concentration exceeds 0.001% in leave-on-the-skin products and 0.01% in products that are rinsed off the skin​.

EU 26 List: The European Union's Regulation 1223/2009 requires that any of 26 substances recognized as allergenic be indicated on the ingredients list for cosmetics products supplied to EU markets. This includes Limonene. These substances must be listed on the container or packaging when present at certain levels: 0.01% in a rinse-off cosmetic (like soap, shower gel, shampoo) and 0.001% in a leave-on cosmetic (like cream, lotion, tonic)​.

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