What is alopecia? Jada Pinkett Smith's experience brings public awareness to disease

Chris Rock made a joke about Jada Pinkett Smith's shaved head at the Oscars, prompting her husband, Will Smith, to jump on stage and slap Rock. The Smiths were apparently upset with the joke – during which Rock likened Pinkett Smith to bald movie character "G.I. Jane" – because she has alopecia, which causes hair loss.

Alopecia is a disease that develops when the body attacks its own hair follicles, which can cause hair loss anywhere on the body, according to the American Academy of Dermatology. Many people with the disease develop a round or oval bald patch on their scalp, but some forms of alopecia can cause total hair loss on the scalp, or even the entire body.

Smith first opened up about her alopecia diagnosis on a 2018 episode of her family's Facebook Watch show "Red Table Talk." She said it was "terrifying" and that she discovered handfuls of her hair were falling out in the shower. "It was one of those times in my life where I was literally shaking in fear. That's why I cut my hair, and why I continue to cut it," she said.