• Health

Hulda Clark’s “zapper” device is based on pseudoscience; doesn’t kill parasites or cure diseases

Posted on:  2024-01-12

Key takeaway

Alternative therapies involve a variety of products and practices that aren’t part of conventional medical care and are used instead of standard treatment. But many of those methods haven’t been adequately tested, and there is little information about their safety and efficacy. This is particularly true for health products marketed online, which are largely unregulated. One main risk of these products is they may discourage patients from seeking life-saving medical treatments. Furthermore, many of them can also cause side effects or interfere with standard medical treatment. In the worst-case scenario, the product itself can be downright dangerous to people.

Reviewed content


A “zapper” can kill parasites, bacteria, and viruses; it cures all diseases

Source: Facebook, TikTok, Hulda Clark, 2024-01-03

Verdict detail

Incorrect: There isn’t one single cause for all diseases. Diseases result from a variety of causes and contributing factors, including infectious agents, genetic mutations, and lifestyle and environmental factors. While parasites cause some diseases, they have no established causal link with many others.
Inadequate support: There is no clinical evidence demonstrating that applying a low-voltage electric device to the body kills parasites or provides any health benefit to people with serious illnesses such as cancer, Alzheimer’s, diabetes, or AIDS.

Full Claim

A “zapper” can kill parasites, bacteria, and viruses; it cures all diseases


Social media is flooded with a vast assortment of supplements, natural remedies, and devices that are touted as complementary or alternative treatments for virtually any disease. Many of these products promise extraordinary health benefits far exceeding those of conventional treatments. However, health products offered online generally lack scientific support and some can pose serious health risks[1,2].

A video posted on the Facebook page “Hulda Regehr Clark, Ph.D., N.D.” on 3 January 2024 is one pervasive example of such products.

Clark was a natural health practitioner who claimed that a single parasite is the cause of all cancers and many other serious diseases, including diabetes, acquired immunodeficiency syndrome (AIDS), and Alzheimer’s. In the 1990s, Clark developed a protocol that purportedly cured these diseases by clearing this parasite from the body. Clark also authored the books “The Cure for All Cancers” and “The Cure for All Diseases”, where she communicated her theories about disease and promoted her methods.

In the Facebook video, Clark explained how to use the “zapper”, an electric device she developed herself that supposedly cures all diseases by clearing parasites from the body. Iterations of Clark’s claims are also common on TikTok, where they accumulate hundreds of thousands of views.

But as we will show below, Clark’s claims are baseless, and experts and medical societies have repeatedly dismissed her ideas as pseudoscience. Yet, her claims persist and the “zapper” continues to be marketed online as a cancer treatment. Moreover, Clark’s therapies couldn’t prevent her from dying of multiple myeloma (a type of blood cancer) in 2009, as her official website documented at the time.

Parasites aren’t the cause of all diseases

In her books, Clark attributed the cause of cancer and many other diseases to the human intestinal fluke (Fasciolopsis buski). This parasite infects the intestines of humans and pigs who eat raw or undercooked aquatic plants contaminated with it. Symptoms range from mild abdominal pain and diarrhea to intestinal obstruction, vomiting, fever, and anemia in the case of heavy infection.

Clark believed that exposure to certain chemicals through foods, drinks, clothes, and other everyday products made some organs more susceptible to this parasite. This, in turn, caused the parasite to migrate from the intestine to those organs, causing disease.

Depending on the organ the parasite invaded, Clark claimed, it could cause different diseases (e.g., cancer in the liver, endometriosis in the uterus, AIDS in the thymus, diabetes in the pancreas, and Alzheimer’s disease in the brain). However, these claims are baseless.

First, F. buski can’t be transmitted from person to person and is mainly restricted to South and Southeast Asia. Therefore, it is a very unlikely cause of infection in Western countries. In spite of this, chronic diseases including cancer and diabetes are leading causes of disability and death in countries like the U.S., contradicting Clark’s claims that the parasite is the one true cause of such diseases.

The more general claim that parasites cause cancer, AIDS, and Alzheimer’s is also incorrect. For example, Clark attributed to parasites some diseases whose causes are well-established and unrelated to parasitic infections. This is the case for AIDS, which is caused by the human immunodeficiency virus (HIV).

While the causes of Alzheimer’s and cancer aren’t yet well understood, autopsies from patients with these conditions don’t indicate parasitic infections in the organs affected. The general scientific consensus is that these conditions arise from the interaction of multiple risk factors, including age, environmental and lifestyle factors, and genetic predisposition.

It is true, however, that certain viruses and parasites can increase a person’s risk of developing some types of cancers, as Health Feedback explained in an earlier review. For example, the World Health Organization’s International Agency for Research on Cancer (IARC) recognizes chronic infection with Schistosoma haematobium, Opistorchus viverrini, and Clonorchis sinensis as cancer-causing (Group 1 carcinogens).

But the fact that some parasites can lead to certain types of cancer is entirely different from claiming that parasites are the sole cause of cancer. F. buski isn’t even included in the IARC list of cancer-causing parasites. And even in the case of cancers resulting from an infection, eliminating the pathogen doesn’t cure the cancer once it has developed.

Clark’s “zapper” has no proven health benefit

Based on the incorrect notion that F. buski causes all diseases, Clark developed a protocol that supposedly cured diseases by clearing the parasite from the body. Using two simple methods, Clark claimed to cure any cancer—and AIDS or other diseases—in only five days.

First, Clark’s books recommended consuming a mixture of black walnut hulls, wormwood, and clove to “cleanse” the gut.

Then came the “zapper”, a device consisting of two copper handles connected to a battery that pulses mild electric currents (nine volts) through the body at a specific frequency (bioresonance). This device is based on the idea that each living organism, including parasites, produces a unique frequency. The “zapper” is supposed to specifically counter the frequency of parasites, killing them without harming human tissues.

However, the theory of bioresonance lacks scientific support, and the “zapper” has never undergone clinical trials to evaluate its effects on cancer patients. There are also no credible reports of people who had been successfully treated or cured of cancer using Clark’s protocol. The principle of the “zapper” is in fact very similar to that of Rife machines, another one of the many electric devices promoted as an alternative to cancer treatment without scientific evidence to support their use.

Therefore, the only evidence supporting Clark’s claims is the cases she described in her books. However, several issues make these reports unreliable.

One issue is whether the cases that Clark described in her books actually had cancer in the first place. The doubt over this matter stems from the fact that Clark didn’t rely on recognized medical criteria for the diagnoses but instead used another self-developed, unvalidated device, the “Syncrometer”. This device could supposedly detect cancer and toxins in affected organs by comparing the sound it emitted when testing the person with the sound emitted when using a “testing substance”.

The Syncrometer is basically a galvanometer, an instrument that detects small electric currents and has no diagnostic value. The testing substances comprised household products containing the “toxic solvents” the person wished to detect in the body, as well as animal parts to identify which organ was affected.

It is also unclear what criteria Clark used to evaluate the outcomes of the people she treated. For example, Clark’s book described several of these people as cured, even though they died weeks after being treated.

In summary, many of these patients possibly had no cancer in the first place, and those who did weren’t followed up adequately to evaluate the effectiveness of the treatment. Therefore, these cases don’t provide any credible evidence to suggest that Clark’s protocol was effective. In contrast, there are well-documented reports of people harmed by Clark’s “zapper”, in the form of burns or by causing interactions with cardiac pacemakers[3].

Even more concerning was Clark’s encouragement to cancel “surgery, radiation, or chemotherapy” because her treatment was “100% effective in stopping cancer regardless of the type of cancer or how terminal it may be”. Following this advice would put people’s lives at risk. Studies have found that refusing standard cancer treatment in favor of pursuing alternative treatments raises the risk of death[1,2].

All these dubious practices ultimately led Clark to face multiple charges in the U.S. and Mexico for negligence and fraud and for practicing medicine without a license.

In 2001, the U.S. Federal Trade Commission (FTC), the U.S. Food and Drug Administration, and Health Canada launched a coordinated initiative called “Operation Cure.All” against the fraudulent marketing of health products on the Internet. As part of this effort, the FTC took legal action against companies marketing “zapper” units based on Clark’s unsubstantiated theories. Several companies were prohibited from making any unsubstantiated claims that her products were effective in treating cancer and any other condition and that the use of these products made surgery or chemotherapy unnecessary.

One of the FTC’s cases was supported by the affidavits of two specialists in cancer and parasitology who explained that Clark’s theories were “based on bad science” and “did not provide competent and reliable” evidence to support her claims.


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