Coumarin is a derivative of the tonka bean, which comes from Dipteryx ordorata, a tree native to Brazil. Some of the organic constituents that make up its flavor are similar to, or the same as, those in pure vanilla. Coumarin is frequently found in synthetic vanillas from Mexico, Central America and the Caribbean as it's cheap and it makes synthetic vanilla taste more like the natural. Unfortunately, coumarin is considered toxic, especially to the liver, and potentially carcinogenic, and has been banned from the United States since the 1950s. (Dicumarol, which is a derivative of coumarin, is the active ingredient in certain blood-thinning medications, and is legal in the United States.)"
For more, browse HERE
I'm not sure that it would appear on the label in either English or Spanish. But if the vanilla is very cheap in price it's certain to be artificial, as we all know that vanilla beans are expensive. The artificial stuff is what they add Coumarin to, though obviously not all brands will do this.
IMO better safe than sorry.