Limonene is a scenting ingredient and solvent found naturally in the rinds of citrus fruits, such as oranges and lemons. This compound is what gives these fruits the fresh, clean scent we all know and love. However, following extraction, exposure to light and air breaks limonene down into a number of oxidation products—these are what can act as irritants for some. Limonene has not been linked to cancer, but may cause allergic reactions or other irritation to the skin or eyes, as well as respiratory and immune systems, with repeated or prolonged use. The Center for Disease Control (CDC) has seen bioaccumulation of D-limonene in fish, but there is currently no evidence of similar occurrences in humans. Although this ingredient is currently under some restricted use in cosmetics, it is still found in a number of products from shampoo to lipstick, and more.
• DL-limonene (Racemic)
• Limonene essential oil