The purification rites

The mikveh, or mikvah, is a ritual bath ("ritualarium") to which Jews go at certain times in keeping with the Torah-laws of purity (ritual cleanliness).

The name of the month of February comes from the Latin word februum, which means purification. The purification ritual of Februa occurred on February 15 in the old Roman calendar.

its done for ritual purification...

A basic purification ritual can be conducted that will eliminate most succubi without harm to the host- they do not infest a host like a virus, but visit repeatedly like a pest. A good purification ritual acts like bug repellent.