Azelaic acid is a type of acid that's found in some grains like rye, wheat, and barley. It's naturally produced by Malassezia furfur (also known as Pityrosporum ovale), a yeast found on healthy skin.

There's arguably no category of skincare ingredients that can do more than direct acids. They're well-known—and beloved—for their ability to do everything from brighten skin to unclog pores. But, ...