The 21-year-old pop singer's May 2 date in Amsterdam and May 4 appearance in Antwerp, Belgium, on her Bangerz tour have been pushed back to June.
A Wednesday news release says Cyrus' symptoms from a severe allergic reaction to antibiotics have returned and doctors will not allow her to travel.
Cyrus was forced to postpone her U.S. tour until August after treatment for a sinus infection went awry, but expected to be able to keep her European tour on track. The news release says Cyrus still expects to make her London appearance on May 6 as planned. The Antwerp show has been rescheduled for June 20 and the Amsterdam concert will be held June 22.