Tallow, a purified fat from cattle and other large mammals, was once the main feedstock used to make soaps and many other cosmetic ingredients. This changed with the arrival of BSE, or mad cow disease, in the late 1980s and early 1990s. BSE is a brain disease that affected some cattle herds and caused a great deal of concern because it was linked with a similar disease in humans. This led to some dramatic changes in the way animal-derived ingredients are handled in all kinds of products, including cosmetics.