There's good information on the Ask Humaworm forum about how people get infected wtih parasites etc. Go to the ask Humaworm, and on the top of the page click on humaworm.com
Most of the herbal dewormers contain the basic same 3 ingredients- Wormwood , Black-Walnut , and cloves. Different formulas add other different ingredients, but the 3 basics are the most important.
Read the Humaworm information about how people get infected, but don't let it freak you out, because we live in the parasites world, and they are everywhere, not just from animals. Not seeing them while deworming doesn't mean you aren't killing them, and their eggs.