The chemical name for coumarin is benzopyrone. The distinctive sweet odor reminds many people of freshly cut grass or hay, and it has been used in perfumes since the late 1800s. In a pure form, this compound has a crystalline structure, and it is said to taste faintly like vanilla. When ingested, it acts as a blood thinner, and it also appears to be effective in treating some tumors. Coumarin has fungicidal properties as well. However, other much safer substances can be used for all of these purposes, although the compound is sometimes used in combination with other blood thinners for medical treatment.