Glitter Herpes is being stuck having glitter all over you for weeks, because you can't get the damned stuff off. The glitter often enjoys getting stuck on the upper parts of your cheek, just where you can see it, so it bugs you the entire time it's there.
The phrase actually originates from Edward Cullen, before he was famous. His dandruff is actually what glitter is. The herpes part is because Edward was contaminated with herpes from sucking the blood of a hooker. This is why he now sucks on animals' blood.
Fred: AW MAN, I GOT GLITTER HERPES.
Edward Cullen: Muahaha...