Katy Perry has admitted that she suffers from obsessive-compulsive disorder (OCD), a condition that can cause people to become upset when their routine is disturbed.
And the I Kissed A Girl hitmaker'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.
"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," the Daily Express quoted her as telling Q magazine.
"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,'" she added.