Aromatic substance obtained from the wood of a tree common to Southeast Asia, Cinnamomum camphora, or manufactured synthetically. When applied to the skin, camphor produces a cooling effect and dilates blood vessels, which can cause skin irritation and dermatitis with repeated Inhaling camphor may cause irritation of the mucous membranes above 2 ppm (parts per million) and respiratory depression. Camphor can also cause skin and eye irritation on contact. In fact, depending on the dose applied, acute poisoning can (and has) occurred (Sources: Molecules, May 2013, pages 5,434-5,554; and British Journal of Dermatology, November 2000, pages 923–929). Clearly, camphor isn't an ingredient to take lightly, though it does have several medicinal applications.