Miley Cyrus is hospitalized after having a "severe allergic reaction to antibiotics," a spokesperson tells CNN. The 21-year-old had to cancel tonight's show in Kansas City, though she was able to tweet from her hospital bed: "Kansas I promise Im as (heartbroken) as you are. I wanted so badly 2 b there 2night." TMZ reports that Cyrus had been out shopping with her mom when she fell ill. She had to cancel a show in North Carolina earlier this month because of the flu. (More Miley Cyrus stories.)