Cyrus, 21, called off upcoming shows in Nashville, Tennessee, on Friday and Louisville, Kentucky, on Saturday. The show in Nashville has been rescheduled for Aug. 7 and Louisville on Aug. 9, Live Nation Entertainment Inc said.
The "Wrecking Ball" singer, who has canceled shows in Kansas City, Missouri, and St. Louis earlier this week, posted a statement on Twitter saying she suffered an allergic reaction to the antibiotic cephalexin.
The North American leg of Cyrus' tour in support of her recent album "Bangerz" began in February and she was scheduled to perform more than 40 dates. The 22-concert European leg of the tour begins on May 2 in Amsterdam.