Citrus Unshiu is a small seedless member of the citrus family. The dried peel is used as an ingredient in many skincare products throughout Asia. This medium-sized citrus fruit is native to Japan. Like all citrus extracts, it contains volatile fragrance chemicals that can be a source of irritation. Of course, it has antioxidant ability as do most plants (Sources: Journal of Agriculture and Food Chemistry, July 2008, pages 5,682-5,690; and Cancer Research, September 2000, pages 5,059-5,066).
There is limited in vitro and animal research demonstrating that citrus unshiu has melanin-inhibiting (skin lightening) properties. Whether or not that benefit can be parlayed to human skin is unknown (Source: Journal of Enzyme Inhibition and Medicinal Chemistry, February 2007 pages 91-98).
Research demonstrates that this ingredient’s primary fragrance components (limonene and linalool) have strong potential to provoke an allergenic and irritant response on the skin (Sources: Contact Dermatitis, 2006 and 2010).