For a start it is quite normal, and healthy for humans to have a certain level of parasites in the body. Secondly, the sources that these folk claim to be getting the parasites from are often very dubious. Call me a cynic if you like, but I can't help but see this as another get-rich-quick scheme by those who see natural health as an opportunity to live off the fears of the gullible. Search the web for some testimonial or "facts" about parasites in humans, and they ALWAYS have an "amazing" product to sell.....
Now, I am not for one moment suggesting that humans don't suffer from parasitical infections, they do. And in the third world it is a major problem. And if we are going to be broad about this, we could call viruses and bacteria parasites, and make the claims that so many people are infested quite plausible. My argument is that this is not a major cause for concern, if basic hygiene (not fanatical hygiene, which has its own problems) and good nutrition are followed. If you have children and animals in your life, especially if you are a homesteader or family farmer and are in close contact with both, it is a good idea to use garlic and cloves in your diet on a regular basis to keep the microbes to a reasonable amount.
Internal parasites, such as worms, take the nutrition from our food intended for us. This leaves us wide open to other illnesses. Therefore if you are generally "run-down" THIS is the time to consider the anti-parasitical treatments. Any of the herbs listed for treating worms in animals can be considered, but please read details of each, with its contraindications and dosage, carefully. Taking even the safest anti-parasitical herbs on an on-going basis without good reason can leave you anaemic, and vulnerable, because many of the beneficial flora in your intestine will be killed. Herbs ARE medicine. Use them wisely, not like candy.
Worms in children are very, very common. Seen as tiny white wigglies in feces, they often cause no symptoms in small numbers in a healthy child. Unfortunately children's hygiene is often lacking. If they scratch their bottoms (worms itch when they wriggle) then put those fingers in their mouths, they transfer worm eggs via their finger nails, and the cycle begins again. A heavy infestation can make a child lethargic, vulnerable to disease, and cause intestinal upsets. Most parents are shocked, disgusted, even ashamed. But this isn't caused by being "dirty". It's caused by mixing with other children whose hygiene is similarly challenged:) Usually fecal samples are taken by your doctor and a drug will be prescribed. These are no more effective than the herbal treatments, and therefore it is very much a matter of personal choice which route to take. If you are able to break the cycle it is possible to rid the child of worms without any treatment at all. But adding one or more or the safe herbs (see each link for details of safety) to the child's diet while breaking the cycle will speed up the process. Also, unless your child already has diarrhea from the infestation, add a gentle natural laxative, such as oat bran, or psyllium to the diet at this time to flush things through!
External parasites such as lice and fleas are not as common on humans as they once were, but epidemics of head lice, and occasionally scabies (body lice) go through schools especially in warm weather. Headlice are easy to eradicate, but need to be caught before a serious infestation occurs or it can a time-consuming process. Lice shampoos and lotions from your pharmacy are increasingly ineffective as the lice become resistant to them, and there is some compelling evidence for them being toxic even used as directed. The real danger lies in people using them incorrectly, which is very common. It is widely thought that the resistance has been caused by people using the shampoos regularly as a preventative measure. I don't even want to think what all those chemicals have done to their bodies...
Lice need air to breathe just like we do. People who swim regularly do not get lice. However a daily shower is not enough, because the lice are still able to find air pockets. A daily bath which includes 10 minutes of ALL of your hair and scalp being underwater WILL prevent head lice taking hold. This is also a feasible cure. However it will take several days to be sure, and I personally recommend use of an oil to smother the lice. Tea Tree Oil is very effective, but any oil will work, even mayonnaise (not "whipped" alternatives, and NOT low-fat!!). It must be massaged into the scalp thoroughly and left on at least 10 minutes. It can be safely left on overnight. Rinsing it out will be a challenge, but it will be 100% effective on all lice. HOWEVER the eggs (nits) MUST be removed individually by hand, or 7 days later they will hatch and start over.
Meanwhile bedding, hats, teddy bears etc need to be washed, either in very hot water, or soaked (fully immersed) for a good half hour in cool water. Items which cannot be laundered should be bagged up in plastic and left overnight in a cold place (or the freezer). Lice cannot live very long in the cold, that's why they like scalps with warm snuggy hair on.
Bald men don't get head lice