Katy Perry suffers from obsessive-compulsive disorder (OCD) - and often "freaks out" over tiny problems.
The I Kissed A Girl hit-maker admits she has the condition, which can cause sufferers to become upset when their routine is disturbed. Perry's OCD is at its worst when she is on tour - and even a small problem like cat hairs on her clothes can cause her to throw a tantrum.
She tells Q magazine, "I certainly have an OCD side when I'm on tour... What are my areas of OCD? Well, if there's broken make-up in my purse I freak out. Also if I am around household pets and some of their fur comes off on my cardigan, then I can get pretty sharp."
"But my worst one is if I see a pair of sunglasses with fingerprints on them. Truly, I cannot stand it. I go ape. 'Oh my God, I can't breathe! Wipe them clean! Agghhh!'"
California Gurls is still number one on the charts, and now Katy has another song roaring up the charts, with Teenage Dream. Get a behind the scenes look with Katy describing what the song means to her!!