More Options

The Fakery of Electrodermal Screening


Stephen Barrett

Skeptical Inquirer Volume 41.5, September/October 2017

The use of galvanometric devices to make health assessments is commonly referred to as electrodermal screening (EDS) or electroacupuncture according to Voll (EAV). Last year, I tested myself with a leading EDS device forty-three times in ten days and found that the results were preposterous. In addition to my experience, this article describes the history of EDS devices and why I believe they should be banned.

Background History

Electrodermal screening devices are said to measure and react to skin resistance to the passage of low-level electrical current. At least forty have been marketed during the past sixty years. Proponents attribute their origin to Reinhold Voll, a West German physician/acupuncturist who asserted that skin resistance is related to the health of the body’s internal organs. In 1958, he combined Chinese acupuncture theory with galvanic skin response measurements to determine what he said was the body’s flow of “electro-magnetic energy” along “acupuncture meridians” (Barrett 2016a).

Voll’s first transistorized model—the Dermatron—was a box with two gauges, several dials, and wired components that would be placed in contact with the patient’s skin. The device emitted a tiny direct current that flowed through a wire to a metallic cylinder that the patient held in one hand. Another wire went from the device to a probe that the operator touched to supposed “acupuncture points” on the patient’s other hand or a foot.

The Dermatron measured the electrical resistance of the patient’s skin at each point touched by the probe and displayed it on a gauge as a number from 0 to 100. Voll declared that readings from 45 to 55 were normal (“balanced”), readings above 55 indicated inflammation of the organ “associated” with the meridian being tested, and readings below 45 suggested “organ stagnation and degeneration.” Homeopathic products would be administered and the patient retested until everything was determined to be “balanced.” Other early devices, such as the Vegatest, added a honeycomb into which vials of remedies could be placed to test whether their contents would supply the hoped-for balance.

Subsequent EAV devices replaced the gauge with a computer that reflected the measurements on its screen, reported what organs might be affected, suggested what products might be most useful, and added dietary supplements and herbal preparations to the recommended product mix. Some systems, most notably the INTERRO, used a dedicated computer, whereas others provided software that would run on a standard computer.

As these evolved, the products being tested in vials were replaced by computer codes said to represent the products, and software was programmed to display elaborate charts, pictures, and lists of body areas, symptoms, diseases, and supposedly corrective measures. Most recent systems don’t use a probe but have the patient continuously connected through one or more components that serve as electrodes. ZYTO devices use a hand cradle that plugs into a computer. The iTOVi Nutrition Tracker uses a hand-held scanner that plugs into a smartphone loaded with an app that generates recommendations (Barrett 2017a).

The INTERRO. One probe is held in the patient’s hand. As the other probe is touched to the patient’s other hand or foot, a bar rises on the right side of the computer screen, accompanied by a noise. The reading supposedly determines the status of various organs of the body. After the alleged problems are “diagnosed,” glass vials containing homeo- pathic solutions are placed in the metal honeycomb and the tests are repeated to determine which will correct the alleged “imbalances.”

I stumbled onto the fakery of these devices during an investigation of homeopathy for Consumer Reports magazine. In 1986, after testing me with an INTERRO device, the clinic proprietor said I had a number of electromagnetic blockages plus “temporomandibular joint stress, probable subclinical allergies, and possible mild early preclinical arthritis” (Barrett 1987). During the testing, I noticed that the harder the probe was pressed against my skin, the higher the reading on the computer screen—which is not surprising, because pressure reduces electrical resistance and makes the current flow better from the probe to the skin. A few years later, I learned that placing products into the honeycomb of a Vegatest device had no effect on its readings (Mosenkis 2001). This was no surprise because glass does not conduct electricity, so even if the products emitted electric signals, they could not escape from the vial.

The current market leader of EDS systems appears to be ZYTO Technologies of Lindon, Utah. Its users include chiropractors; naturopaths; acupuncturists; massage and colon therapists; “holistic” dentists; veterinarians; physicians who purport to practice “integrative” or “complementary” medicine; and unlicensed “nutritional consultants,” “wellness consultants,” “health coaches,” and distributors for multilevel marketing companies that sell dietary supplements and/or herbal products.

ZYTO’s Claims

According to the ZYTO website, “Just like a doctor uses a stethoscope to listen to a child’s breathing, the ZYTO ‘listens’ to the body’s subtle galvanic skin response” and suggests corrective measures (ZYTO 2017b).

To run the test, the hand cradle is connected to a USB port on the practitioner’s computer, and the patient’s hand is placed with palm and fingers touching corresponding metallic areas on the device. The practitioner then launches the software program and selects the type and scope of test from menus that appear on the computer screen. The software then generates numbers and graphics that supposedly indicate (a) whether the function of various organs and body parts are “in range” (favorable) or “out of range” (unfavorable) and (b) which products, procedures, and/or dietary measures show the most “coherent responses” (those that will bring the values “within range”). Changes in skin resistance are said to trigger what gets matched.

ZYTO says that its software sends “digital signatures” (unique code numbers) to the body and determines “the body’s degree of preference” for measures that will make the body most “biologically coherent.” To have their products considered during the test process, manufacturers submit them to the company, which creates a “library” of digital signatures for each product plus a brief description of what the product can do. “Libraries” are available for the offerings of more than 200 companies. ZYTO’s software is also said to contain signatures that represent the condition of various organs, teeth, and spinal segments—all of which, the company claims, are connected through acupuncture meridians (ZYTO 2017a).

The stated goal of the test is to match the supposed characteristics of the patient to the products, services, and/or dietary advice that the practitioner can provide. The Internet-advertised prices of scans run from $10 to $250, but the recommended products often cost hundreds of dollars more. Testing can be done in the presence of the practitioner or done remotely though the Internet by connecting a purchased or borrowed hand cradle to the client’s computer. Many practitioners aim to scan everyone who consults them. One provider in Virginia, who has no relevant license but offers remote testing throughout the world, states that he has done more than 20,000 scans.

Last year, I was able to access a ZYTO system (the Elite 5.0) and see whether repeated testing could produce consistent and meaningful results (Barrett 2017b). As far as I know, no similar study has ever been published.

My Test Results

Using myself as the subject, I ran three series of tests. The first was a basic scan that supposedly evaluated my internal organs. The other two were nutritional “biosurveys” to determine what I should or shouldn’t eat.

The basic scan is said to determine whether “biomarkers” are in or out of range for twenty organs: adrenals, bladder, gallbladder, heart, hypothalamus gland, kidneys, large intestine, liver, lung, pancreas, parathyroid, pineal, pituitary, prostate, small intestine, spleen, stomach, testes, thymus, and thyroid. My basic scans generated reports that were eight to thirteen pages long. Shown below are portions of six pages from one of my reports. The findings for the organ biomarkers are displayed with a colorful full-page bar graph and as positive or negative numbers elsewhere in the reports.

Selected pages from a ZYTO report

The colorful bar graph purports to show whether biomarkers for each of twenty organs are “out of range.” The greater the supposed problem, the longer and redder the bar that crosses the vertical “range line” in the middle of the bar graph. Most scans have a bar for every organ, but this one failed to detect the author’s adrenal glands, prostate, and testes. The other pages state which spinal segments, acupuncture meridians, or teeth have relevant problems and which products can correct the alleged problems.

Table 1 shows the results of sixteen basic scans, with four done within an hour on each of four consecutive days. These scans found means of 69.2 biomarkers and 11.4 organs that were “out of range,” but the organs specified and the supposedly corrective products—a mean of 5.3 per scan—varied considerably from one test to another. The organ with the highest “out-of-range” score, positive or negative, also differed from test to test. Four reports highlighted my adrenal glands; three chose my small intestine; two chose my heart; two chose my thymus; and the other six tests each identified a different, supposedly problematic, organ. Only four of the sixteen scans had any organs “within range.”

The numbers are said to represent the body’s response to code numbers that represent the organs listed in column 1. The soft- ware determines a range (baseline) value, compares the response numbers with that value, determines whether “biomarkers” are within that range,” and recommends products that supposedly will bring “out of range” biomarkers back “in range.” ZYTO reports list the “out-of-range” numbers in a table. The numerical value of the “in range” numbers can be derived by measuring the bars in the bar graph, but their direction is not specified, so they are listed here as “±” numbers. The furthest out-of-range numbers (displayed here in bold-face type) are said to require the most attention. If a table cell is empty, no organ response was reported. All numbers are rounded to the nearest integer.

Even though I have no gallbladder, this organ was reported to be positively “out of range” four times, negatively “out of range” four times, and “within range” eight times. I have benign prostatic hypertrophy, but my prostate did not show up in one scan and was reported to be positively out-of range in seven, negatively out of range in four, and within range in four.

ZYTO claims that its nutritional surveys can determine “which foods and supplements are right for you” (ZYTO 2016). The test reports can be configured to assess food categories, “top negative foods,” and/or “all positive in-range foods.” The food categories are additives, beans/legumes, beverages, dairy/egg, fat/oils, fish/seafood, fruits, grains, meats/poultry, miscellaneous, nuts/seeds, spices/seasonings, sugars/sweeteners, and vegetables.

To explore how the food biosurveys work, I conducted twelve food-category tests and fifteen individual-food assessments. The resultant reports were two to four pages long.

The food-category tests were completed within one hour. As shown in Table 2, the test reports recommended avoiding a mean of 6.4 categories per test, but not necessarily the same ones. Ten of these tests recommended avoiding grains, nine recommended avoiding nuts and seeds, and eight recommended avoiding fruits and vegetables. Five recommended avoiding all fruits, vegetables, and grains. One recommended only sugars/sweeteners; one recommended only beans/legumes; and one recommended only beverages, fish/seafood, meats/poultry, and spices/seasonings.

The numbers are said to quantify the body’s response to code numbers that represent the listed food categories. The positive numbers are food categories that should be included in your diet. The negative numbers represent the “top negative foods” that should be avoided. The “Avoid” column is the number of times the “top negative” list included the group. All numbers are rounded to the nearest integer.

The individual-food tests were done in two groups. First, there were ten tests that assessed common foods. Two days later, five tests assessed a larger food list. Both groups took less than an hour to complete. As with the basic scans, the individual-food scores were wildly inconsistent, with many foods scoring “positive” (recommended) on one test and “negative” (not recommended) on another administered a few minutes later. For example, pineapple and red potatoes were listed seven times among the top negative foods and three times among the most positive foods.

The claim that ZYTO scanning can provide clinically useful information is preposterous. To demonstrate that a device is capable of measuring something, it is necessary to validate its accuracy and consistency with repeated tests. My basic scan results were so inconsistent that they could not possibly be clinically meaningful. In addition to being inconsistent, my food-category biosurveys recommended excluding so many foods that the resultant diets could be extremely unhealthful. Statistic analysis using Cohen’s kappa to compare the results to one another found that they did not differ significantly from random.

To demonstrate that a device can detect organ pathology, it is necessary to do controlled studies of people who have that condition and people who do not. To demonstrate that administering a product or procedure can improve outcome, it is necessary to study whether people who are treated do better than similar people who are not. A Medline search for “ZYTO” in the title yields no relevant publication.

ZYTO Technologies has not explained how it can construct or validate its organ assessments or product libraries without any underlying clinical studies. Nor is there any logical reason to believe that skin resistance is related to organ health or what people should eat. But even if magical explanations were found, the ZYTO system’s moment-to-moment variability would still render its findings useless.

Electrodermal screening tests are not only worthless but potentially harmful. In addition to money wasted on the test and useless products, the harm can include (a) needless worry about nonexistent medical problems suggested by the test reports, (b) the cost of medical care involved in seeking reassurance, (c) failure to seek appropriate medical care for real problems, and (d) the consequences of malnutrition due to excessive dietary restrictions.

Government Regulation

In 2011, ZYTO Technologies obtained 510(k) clearance from the FDA to market its hand cradle as a galvanic skin response measurement device (Eydelman 2011). Clearance merely requires “substantial equivalence” to a device that was previously cleared or approved. It is not the same thing as approval, which requires that clinical trials demonstrate safety and efficacy for its intended purpose.

Because moistness of the skin affects its ability to conduct an electrical current, a few galvanic skin resistance devices have legitimate medical use in managing sweat-gland disorders. Aside from this, however, skin resistance has no proven or logical relationship to the diagnosis or management of any medical problem. ZYTO’s 510(k) application and software registration did not indicate that the device would be used for diagnostic purposes.

ZYTO’s marketing materials state that its devices are “not intended to be used in the diagnosis, cure, treatment, mitigation, or prevention of any disease or medical condition.” However, “intended use” is based on the context in which a device is used and is not necessarily changed by the use of disclaimers or contrived terminology.

In 2015, the FDA warned ZYTO Technologies Inc. that “the promotion of the ZYTO Hand Cradle for use in diagnosing a disease or condition, predicting biological responses to a wide range of virtual stimuli including drugs and nutritional supplements . . . fall outside of the device’s cleared intended use to measure galvanic skin response and constitutes a major change or modification to the device’s intended use.” The FDA also objected to the claim that “ZYTO’s technology measures your body’s responses to a specific library of nutritional products, asking your body which it prefers” (Mitchell 2015).

In 2016, presumably as a result of FDA pressure, ZYTO Technologies announced a voluntary recall of 1,252 ZYTO Select and Elite software programs due to “claims exceeding the 510(k) clearance” (FDA 2016). ZYTO has modified some of its marketing language, but there is no reason to believe this will influence how practitioners use its devices.

Marketers of the iTOVi Nutrition Tracker state that it is a “general wellness device” that does not require FDA clearance or approval. Some of its claims are similar to the language used by ZYTO to which the FDA objected, but whether the FDA will do anything about the iTOVi remains to be seen. The use of EDS devices by practitioners is subject to regulation by the states. Some states have taken disciplinary action, but there has been no systematic effort to discourage EDS use (Barrett 2016b).

There is no scientific evidence or logical reason to believe that galvanic skin response testing can determine a person’s health status or strategies for health improvement. I believe that all such devices and associated software that are used for these purposes should be removed from the marketplace. •


Stephen Barrett

Stephen Barrett, M.D., a retired psychiatrist, operates, dedicated to debunking dubious health information on the Web and elsewhere. He is also Vice President of the National Council Against Health Fraud, and a Fellow of the Committee for Skeptical Inquiry.