A thick viscous grey-black fluid clings to the stoppered vial. The alchemist claimed the viscosity was necessary to give the draught time to work. Apparently lacking a functioning alimentary canal has it's draw backs
When consumed, the undying unguent restores 2d4+2 hit points to any undead creature. 

The greater undying unguent restores 4d4+4 hit points to any undead creature.

Living creatures who consume the undying unguent, taking an equivalent amount of damage and are sickened for 1d4 hours. Vomiting, flushing with water, and similar non magical interventions are in effective at purging the unguent.