Abstract:A new six-membered α,β-unsaturated lactone, lacquer allergic lactone, was isolated from the nonphenolic portion of chinese lacquer. Based on the result of clinical test on human bodies, it was an allergenically active volatile compound. The structure of this lactone was identified by means of IR, MS, NMR and chemical reaction. The urushiols was not the unique allergic principle since the actone was isolated.