I, too was very sceptical. Did not think I had any parasites. Tests did not show any. But I know about the unreliability of tests. I had no absolute guarantees that I had none, so I did the parasite cleanse, "Just in case", and because Hulda Clark recommends in her book " A cure for all Disease", to do it before a liver flush. After my 3rd Liver Flush I was in absolute shock! I had not expected parasites, but there they were, quite visible!(I'll spare you and me the details). I could not live in denial any longer.
Tell your wife to look at it like an insurance policy. We take out car and house and health insurance policies without "guaranties" that we will actually need them. But when we do, we are sure glad we got the insurance...