Bitter Fennel oil, also known as Common Fennel oil, has spicy, herbal, and anisic olfactory characteristics similar to licorice. Chemically it is quite similar to Sweet Fennel, but with a high anethole content that creates a spicier and less sweet aroma. Fennel oil is often used in skincare products, digestive aids, immune supports, and stimulating aromatherapy blends.