The U.S. Food and Drug Administration lists castoreum as a “generally regarded as safe” additive, and manufacturers have been using it extensively in perfumes and foods for at least 80 years, according to National Geographic and a study in the International Journal of Toxicology. “I tell them, ‘Oh, but it’s beavers; it smells really good.’” 
 
 Castoreum is a chemical compound that mostly comes from a beaver’s castor sacs, which are located between the pelvis and the base of the tail. Because of its close proximity to the anal glands, castoreum is often a combination of castor gland secretions, anal gland secretions, and urine. As one can surmise, the vanilla aroma is not typical of the area, but is a product of the beaver’s unique diet of leaves and bark, said Joanne Crawford, a wildlife ecologist at Southern Illinois University, speaking to National Geographic. The chemical compound that beavers use to mark their territory has a musky, vanilla scent, which is why some perfume makers incorporate the component into their products and food scientists add the all-natural ingredient into recipes. “You can milk the anal glands so you can extract the fluid,” Crawford said. “You can squirt [castoreum] out. It’s pretty gross.” 
 
 Due to such unpleasantness for both parties, castoreum consumption is rather small—only about 292 pounds (132 kilograms) yearly. According to Fenaroli’s Handbook of Flavor Ingredients, published in 2005, total annual consumption of both castoreum extract and castoreum liquid was around 250 pounds, undoubtedly because the milking process is unpleasant for all parties involved. Because the FDA considers the ingredient safe, in some cases, manufacturers don’t have to list castoreum on the ingredient list and may instead refer to it simply as “natural flavoring.” Apparently “gross” is not something the FDA quantifies.
– Like vanilla ice cream? Don't read this—because the smell of a beaver's butt is key to at least some vanilla flavoring, Time reports. More specifically, beavers like to mark their territory with a musky, vanilla compound located in sacs between the pelvis and the base of the tail. Manufacturers have been extracting it for 80 years to flavor foods and perfumes—but it's tricky, because the compound often mixes with urine and anal gland secretions. "You can milk the anal glands so you can extract the fluid," wildlife ecologist Joanne Crawford tells National Geographic. "You can squirt it out. It’s pretty gross." But she admits to sticking her nose in there and taking a whiff: "People think I’m nuts. I tell them, 'Oh, but it’s beavers; it smells really good.'" For the record, the slimey brown compound is extracted by anesthetizing a beaver and "milking" its nether regions. Ice cream sundae, anyone?