Completely untrue, in my experience, at the beginning.
I saw my PCP.
The itchy buttock rash was gone when I saw him.
He thinks the rash would last longer if was Dermatitis Herpetiformis and not come and go so fast.
Beware - when it decides to stay, it's hellish.
That said, it wouldn't disappear daily. It would stay a week or two, vanish. Then 6 months, vanish. Then, it didn't go away....