Methyl salicylate (oil of wintergreen) is a natural product of many species of plants. Some of the plants producing it are called wintergreens, hence the common name. It is used as a rubefacient in deep heating liniments, and in small amounts as a flavoring agent at no more than 0.04%. It is also used to provide fragrance to various products and as an odor masking agent for some organophosphate pesticides. If applied in too high quantities it can cause stomach and kidney problems. It is one of many compounds that is attractive to males of various species of orchid bees, who apparently gather the chemical to synthesize pheromones; it is commonly used as bait to attract and collect these bees for study. Methyl salicylate also has the ability to clear plant or animal tissue samples of color, and as such is useful for microscopy and immunohistochemistry when excess pigments obscure structures or block light in the tissue being examined. This clearing generally only takes a few minutes, but the tissue must first be dehydrated in alcohol. Methyl salicylate, though its source plants are not true mints, is also used as a mint in some kinds of chewing gum and candy, as an alternative to the more common peppermint and spearmint oils. It can also be found as a flavoring of root beer. It is also a potentially entertaining source of triboluminescence; when mixed with sugar and dried, it gains the tendency to build up electrical charge when ground. This effect can be observed by crushing wintergreen Life Savers candy in a dark room. Methyl salicylate can also be used as a transfer agent, to produce a manual copy of an image on a surface. Methyl salicylate is added in small amounts to glacial acetic acid to lower its freezing point while travelling in cold countries. Methyl salicylate is also used as a simulant or surrogate for the research and investigation of the chemical warfare agent, sulfur mustard due to its similar chemical and physical properties. Methyl salicylate is one of several antiseptic ingredients in Listerine mouthwash produced by the Johnson & Johnson company.