"Warning! Herbal Colon Cleansers May be Harmful!"
http://www.oxypowder.com/articles/warning-herbal-cleanser.html
Dangers of using Psyllium
http://www.colon-cleanse-constipation.com/psyllium-research.html
Dangers of using Cascara Sagrada
http://www.colon-cleanse-constipation.com/cascara-sagrada-research.html