Notions of internal cleansing had resurgence along with the rise of alternative medicine in the 1970s and following; it remains unscientific and anachronistic. With the rise of the environmentalist movement, many detox diets use the diet format as a political platform to advocate for environmental ideas about pollution and toxic contamination. Finally, keep in mind that fad diets aren't a good long-term solution.
For lasting results, your best bet is to eat a healthy diet based on fruits and vegetables, whole grains, and lean sources of protein. Detoxification diets are popular, but there is little evidence that they eliminate toxins from your body.