What is alopecia? The hair loss condition explained after the Will Smith Oscars controversy

Will Smith and wife Jada Pinkett Smith attending the Vanity Fair Oscar Party (Doug Peters/PA)
In one of the most controversial incidents in Academy Awards history, Will Smith stormed the stage and slapped Chris Rock after the host made a joke about wife Jada Pinkett Smith’s hair loss.
The actor, who apologised to the Academy and his fellow nominees while accepting the best actor award for King Richard, appeared to take offence to Rock quipping: “Jada can’t wait for GI Jane 2,” referring to the Red Table Talk host’s buzzcut.