Miley Cyrus on Allergic Reaction -- 'I Was Poisoning Myself'

Miley Cyrus is sticking to her story ... it was an allergic reaction that put her in the hospital for a week ... saying the whole ordeal drove her "insane."

Miley called into Ryan Seacrest's radio show on Monday, where she detailed how she ended up so sick: "I was on this medicine for five days and everything was all good and on the sixth day, I just woke up … it was so scary … I had basically been poisoning myself with something I didn’t know I was really scary allergic to and it was so scary."

She cancelled several tour dates while laid up, said she was crying all the time because she was so bored and passed the time by online shopping.