"Colon cleansing is a process where the colon is 'cleansed' by inserting two tubes into the anus and up the colon. One flushes with water (and sometimes vitamins, herbs, tea, etc.) while the other tube suctions out the diluted feces," said Dr. Anna Guanche, a dermatologist with the Bella Skin Institute.
The amount of fluids flushed through the system in a single colonic can reach as much as 16 gallons. Sometimes cleaning the colon is a necessary preemptive measure a doctor prescribes before a medical procedure, such as a colonoscopy, or in cases of severe constipation. However, in recent years, it's become somewhat trendy to voluntary have one done.