The original plant of Citrus hassaku Hort. Tanaka was found at the Jyoudo Temple in Inno-shima, Hiroshima Prefecture, Japan by Ekei Shounin in the Edo Era. Citrus hassaku has been called "jagada" when it was first discovered. Since this fruit was seasoned for eating around "hassaku" (August 1st of the lunar calendar), it was given the scientific name as "C. hassaku." Today, the fresh raw fruits of C. Hassaku are cultivated as a seasonal food, and the most famous producing district of C. hassaku fruit is Wakayama Prefecture, representing about 60% of the Japanese output. The immature fruits of C. hassaku and its three main flavanone glycosides (naringin, neohesperidin and narirutin) was found to shown inhibitory activities on a compound 48/80 induced histamine released from mast cells, and anti-allergic effects on dinitrofluorobenzen (DNFB)-induced triphasic skin reactions in mice. The contents of the three flavanone glycosides in the immature fruits were higher than those in mature fruits. The application of extracts from the immature fruits of C. hassaku to skin care for patients with atopitic dermatitis has resulted in improving effects for 76% of the patients. Similar efficacy was obtained for patients pollinosis.