According to Billboard, Cyrus has been forced to postpone tour dates in Nashville on Friday (April 18) and in Louisville Saturday. The singer previously canceled dates Tuesday in Kansas City and Wednesday in St. Louis, as reported by Radio.com.

Cyrus posted an official statement to her Twitter today, which notes that she had been suffering from a sinus infection, for which she took medicine - Cephalexin - that eventually gave her an allergic reaction.

"This type of extreme reaction can last from five to 27 days in these types of cases," the statement notes. "She will remain hospitalized and is under a doctor's care until we see some improvement in her condition and is asking for your compassion and privacy at this time. Miley is devastated about missing shows and possibly disappointing her fans."