The cause of the reaction was unknown, but he was being held overnight at Ronald Reagan UCLA Medical Center for observation and was in stable condition.
Powell, a 6-foot-4 guard, began puffing up, had trouble breathing and broke into hives during the afternoon practice session, but doctors were able to control the symptoms, a school spokesman said. He will not practice Thursday and will be monitored daily. The Bruins next play Saturday against Pennsylvania at the Honda Center in Anaheim.
Peter Yoon covers UCLA for ESPNLosAngeles.com.