Ginseng (the root of Panax ginseng CA Meyer, family Araliacease), which is used in Korea, China and Japan as a herbal medicine, was fermented with Ganoderma lucidum (GL) and their antiallergic effects were investigated. Of GLs used for fermentation, KCTC 6283 potently produced ginsenoside Rh2, followed by KFRI M101. KCTC 6532, and ginsenoside Rd, followed by KFRI M101. Oral administration of these fermented ginseng extracts inhibited allergic reactions, passive cutaneous anaphylaxis reaction induced by IgE and scratching behaviors induced by compound 48/80. Of them, the ginseng extract fermented by KCTC 6532 and KFRI M101 potently inhibited allergic reactions compared to that fermented by KCTC 6283. These findings suggest that the fermentation of ginseng with GL can increase its antiallergic activity and the increment of its antiallergic effect may be due to the biotransformation of ginseng saponins to ginsenosides Rd and Rh2.