Bath Time is a symptom combo exclusive to the Necroa Virus DLC which causes cannibal assaults to happen, increasing infectivity. Autophagia, Polyphagia, and Cannibalism are required. The achievement Tasty is earned for forming the combo. This is tough to obtain, and may require multiple tries.
Trivia
This combo (and its name in particular) references the 2012 "bath salts" incident in Miami. The victims had their faces chewed off by people who took the drug. Template:Symptomcomboboxnav