Limonene Worst Fragrance Synthetic and Natural No known benefits Limonene description Chemical constituent of many natural fragrant ingredients, notably citrus oils such as lemon (d-limonene) and pine trees or species of the mint family (l-limonene). Topically, limonene can cause sensitivity and is best avoided. Also, because of its penetration-enhancing effects on skin, it’s particularly important to avoid products that contain limonene plus other skin sensitiser like denatured alcohol. Like most volatile fragrance components, limonene also has strong antioxidant benefits and has also been shown to calm skin; however, when exposed to air these highly volatile antioxidant compounds oxidise and become capable of sensitising skin.