Eithreium is an ogre enzyme used for tracking. It is not commonly used because it's weaker, but it is completely odorless, making it undetectable. Using reveldust, it is said to glow pink, indicating ethreium. A remedy for this is spreading voracillius on your affected area and letting it gobble up the eithreium like candy. Melting off the exposed skin also appears to be a potential way to remove it.