What? Xanthan Gum is made by fermenting corn sugar with a bacteria, Xanthomonas campestris. It is the same bacteria that creates black spots on broccoli and cauliflower. Xanthan gum is an emulsifier. It helps ingredients blend more effectively and stay blended while waiting on a shelf. You need to add a very small amount of xanthan gum to a cream-based product in order to keep the individual ingredients from separating. Xanthan gum is also used as a thickener. Add a bit to water and it becomes more viscous.
Why? Another use for xanthan gum is the stabilization and binding of cosmetic products. One advantage of xanthan gum is that a little goes an incredibly long way; cosmetic manufacturers only have to add a very small amount of xanthan gum to their cream-based products in order to keep the individual ingredients from separating. Despite the use of bacteria during processing, xanthan gum itself is not generally harmful to human skin or digestive systems, though some individuals may find they are allergic to it.