Still early days in my self-experimentation, but I've just started a 2-3 week trial of colloidal silver, as prescribed by my osteopath. I'm not taking it as an anti-parasitic, although I'm sure (if it works) it will take care of any nasties I have living inside. I have ankylosing spondylitis, and antibiotics have been known to help in some cases.
Word of warning: if you Google it, you'll find all manner of freaky pictures of people with blue skin and testimonials that say it made them grow a third arm (not really). If you're interested, speak with a naturopath or someone who's actually works with it.
Effects have been neutral in week one, and I haven't turned into a Smurf yet, so here's hoping.