Hanna Kroeger MsD is a cross between a nutritionist and a new ager. She has been an annual speaker at the National Health Federation Conventions. I found this short book to be a great primer on the five classes of parasites, where they come from and what symptoms they cause. She offers an herbal alternative to the medical theory of 'differential toxicity' in which poisons are admisitered to the body in low enough amounts to be lethal only to the invaders. Interesting.