My 8 year old woke up with discharge in her underwear this morning. gooey whiteish substance. what could it be? she has no breast tissue yet.

Foreign body reactn: At that age with no signs of development there is a good chance the kid has retained foreign material in their vagina. Sometimes a piece of toilet tissue or other debris will make it inside. If you spread the labia and paddle some water into the area it may float something out. She may need to have it checked out if the drainage is foul or persists.