The Facebook application for the iTouch and iPhone allows you to chat with contacts, post photos and videos, update your status and post notes. When you chat with a contact, Facebook saves your chat history for later reference. When you sign off or close the application, the chat history still remains, and the application requires you manually delete each conversation.
Tap "Facebook" on your iTouch's application list and enter your login information if you haven't already logged in.
Tap the "Home" icon in the top left corner of the window to view the application's main menu. Tap "Chat" and slide your finger to the contact whose chat history you want to delete.
Tap "Delete" to erase the chat history for that contact.