10 Terrifying Medical Mysteries That Turned Out to Be Poisoning

A sudden outbreak of unexplained physical symptoms can be terrifying. Today, doctors can test for countless pathogens, chemicals, and environmental contaminants. Throughout much of history, however, physicians lacked modern toxicology to help them investigate mysterious illnesses. People might blame strange symptoms on contagion, nutritional deficiencies, hereditary disorders, or even curses.

In some cases, investigators took decades or centuries to identify the real culprit. Entire communities suffered while doctors searched for diseases that did not exist, unaware that something in the victims’ food, medicine, workplace, or environment was slowly poisoning them. Investigators eventually traced these ten frightening medical mysteries to toxins hiding in plain sight.

Related: 10 Mysteries of the Human Genome

10 Minamata’s Dancing Cats

In 1956, a five-year-old girl was admitted to the hospital operated by the Chisso Corporation in Minamata, Japan. Her legs could not support her, her speech was slurred, and she suffered repeated convulsions. Two days later, her younger sister arrived with similar symptoms. A neighbor’s daughter also became ill, and doctors soon identified several more patients with the same mysterious neurological condition.

Something equally disturbing had already been happening to Minamata’s animals. Cats staggered, convulsed, and thrashed uncontrollably. Some reportedly hurled themselves into the sea. Locals called the phenomenon “cat dancing disease.” When people began displaying similar symptoms, doctors feared an outbreak of a contagious brain disease and isolated patients.

Investigators noticed that the illness was concentrated among fishing families whose members—and pets—ate large quantities of local seafood. Research eventually revealed that wastewater from Chisso’s chemical factory contained methylmercury produced during acetaldehyde manufacturing. The mercury accumulated in fish and shellfish, then entered the bodies of the people and animals that ate them.

Japan officially recognized the outbreak in 1956, although later research identified an earlier patient who became ill in 1953. The catastrophe became known as Minamata disease, one of the world’s most infamous cases of industrial poisoning.^[1]

9 The Jake Walk Epidemic

During Prohibition, tens of thousands of Americans across the South and Midwest developed a baffling neurological condition. Their hands and feet weakened, and many lost control of their lower-leg muscles. Victims were left with a distinctive foot-dragging, high-stepping gait that became known as the “Jake Walk” or “Jake Leg.”

Doctors initially struggled to explain the sudden wave of paralysis. The symptoms resembled those produced by several neurological diseases, but many patients concealed one important fact: They had been drinking Jamaica ginger extract, commonly called “jake.”

Although sold as a patent medicine, Jamaica ginger contained enough alcohol to make it popular with people seeking a legal drink. Government regulations required the extract to contain a certain amount of ginger solids, so some manufacturers adulterated their products with tri-ortho-cresyl phosphate, or TOCP. The industrial chemical helped the drink pass government tests but caused delayed and sometimes permanent nerve damage.

The epidemic emerged in 1930, and investigators eventually traced the contaminated products to manufacturers Harry Gross and Max Reisman of Hub Products. The embarrassing circumstances surrounding the poisoning meant many victims remained silent, making the true number affected impossible to determine.^[2]

8 Devonshire Colic

For decades, residents of Devonshire, England, suffered recurring attacks of severe abdominal pain, constipation, vomiting, and muscle spasms. In particularly serious cases, patients developed weakness or paralysis in their hands and wrists. Doctors called the mysterious illness Devonshire colic, but the name did little to explain its cause.

Some physicians blamed the coastal climate. Others suspected gastrointestinal infections or the supposedly acidic fruit local residents ate. The answer finally emerged in 1767, when physician George Baker investigated why the condition was common in Devonshire but rare in neighboring counties.

Baker noticed an important regional difference: Devonshire produced and consumed enormous quantities of apple cider. During cider production, manufacturers used lead in parts of their presses, mills, storage vessels, and other equipment. The acidic juice came into contact with the metal and became contaminated.

By comparing local practices and testing cider for lead, Baker showed that Devonshire colic wasn’t a regional disease. It was lead poisoning delivered one drink at a time.^[3]

7 Itai-Itai Disease

Beginning in the early 20th century, people living in Japan’s Jintsu River basin developed excruciating joint and spinal pain. Many of the worst-affected patients were older or postmenopausal women. Their bones weakened until ordinary movement could cause fractures, while some also suffered serious kidney damage.

The victims’ cries of pain gave the illness its name: Itai-Itai disease, meaning “It hurts! It hurts!” Doctors proposed arthritis, malnutrition, hormonal changes, and vitamin deficiencies as possible explanations. In 1955, the disease was first reported to a medical society as an illness of unknown origin.

The actual cause was industrial cadmium. Wastewater from the Kamioka mining complex upstream had contaminated the river. Farmers used that water to irrigate their rice paddies, allowing cadmium to enter a staple food consumed throughout the region.

In 1968, Japan’s Ministry of Health and Welfare officially concluded that chronic cadmium poisoning had damaged patients’ kidneys and led to osteomalacia, the severe softening of their bones. Pregnancy, aging, calcium deficiencies, and other factors could make sufferers still more vulnerable, helping explain why the disease devastated certain women so severely.^[4]

6 Arsenic Wallpaper Poisoning

Victorian consumers adored brilliant green clothing, toys, furnishings, and wallpaper. Manufacturers supplied that demand with pigments such as Scheele’s Green, a copper arsenite compound, and Paris Green, a related but distinct arsenic-based color. These pigments were inexpensive, vivid, and alarmingly toxic.

People exposed to arsenical products reported stomach problems, skin lesions, irritated eyes, headaches, weakness, and respiratory complaints. Because arsenic poisoning could resemble common gastrointestinal illnesses or cause a gradual decline in health, doctors did not always recognize the connection. The danger was especially severe for workers who manufactured green artificial flowers, fabrics, and wallpaper, inhaling arsenic-laden dust or transferring it from their hands to their mouths.

Wallpaper presented a more controversial problem. Arsenic-containing particles could flake or rub off its surface, and scientists also investigated whether damp conditions let microorganisms release volatile arsenic compounds. The precise importance of those gases remains debated, so the popular image of wallpaper constantly filling rooms with clouds of arsenic gas is too simple.

The underlying danger, however, was real. Arsenic had found its way into wallpaper, clothing, sweets, toys, and numerous other household products. What looked like a fashionable room could therefore expose its occupants to one of the Victorian era’s most common poisons.^[5]

5 St. Anthony’ Fire

Throughout the Middle Ages, terrifying outbreaks swept through European communities without warning. Victims experienced intense burning sensations in their arms and legs, followed by muscle spasms, convulsions, delirium, and hallucinations. In severe cases, blood flow to their extremities stopped. Fingers, toes, and entire limbs blackened with dry gangrene and sometimes fell away.

With no obvious explanation, people blamed contagious disease, demonic possession, or divine punishment. Many sufferers traveled to hospitals and shrines operated by the Order of Saint Anthony, whose members became known for caring for victims. The mysterious affliction acquired several names, including “holy fire” and “St. Anthony’s fire.”

Not every medieval outbreak described by those names can be diagnosed with certainty today. However, many were almost certainly cases of ergotism caused by eating grain infected with Claviceps purpurea. The fungus commonly attacks rye and produces dark structures containing poisonous alkaloids.

Once contaminated grain was milled into flour and eaten, those alkaloids could cause convulsions, hallucinations, and extreme constriction of the blood vessels. The resulting loss of circulation explained both the victims’ burning agony and the gangrene that appeared to consume their bodies.^[6]

4 Pink Disease

In the first half of the 20th century, pediatricians in Europe, North America, and Australia faced a frightening illness that affected infants and young children. Previously healthy children developed painful, pink discoloration and swelling in their hands and feet. Their skin peeled, their hearts raced, and they became unusually sensitive to light.

Many also suffered excessive sweating, irritability, weakness, insomnia, and loss of hair or teeth. Doctors called the condition acrodynia or “pink disease,” but they disagreed about its cause. Proposed explanations included vitamin deficiencies, glandular disorders, infections, and abnormal sensitivity of the nervous system.

In 1948, physicians Josef Warkany and Donald Hubbard reported finding unusually high concentrations of mercury in urine collected from children with the disease. Investigators then began looking at the medicines parents routinely gave their babies.

Many teething powders, laxatives, and worm treatments contained calomel, or mercurous chloride. Repeated doses exposed children to mercury, although only a small percentage of those exposed developed pink disease. That inconsistency had helped hide the connection.

Once doctors removed calomel from most teething powders in the 1950s, the incidence of pink disease declined dramatically. What doctors had treated as a mysterious childhood disorder was largely an epidemic of poisoning caused by trusted household medicines.^[7]

3 Toxic Oil Syndrome

In the spring of 1981, an eight-year-old boy near Madrid died after developing what appeared to be a severe respiratory illness. Within weeks, hospitals were overwhelmed by patients suffering from fever, breathing difficulties, muscle pain, weakness, skin rashes, and abnormally high numbers of eosinophils, a type of white blood cell.

The illness initially resembled an unusual form of pneumonia. Spanish health officials feared a contagious epidemic, and the public panicked while doctors searched for a pathogen. However, the disease did not spread like an infection. It clustered in families that had purchased inexpensive cooking oil from traveling street vendors.

Investigators discovered that importers had obtained rapeseed oil intended for industrial use. The oil had been denatured with aniline so that it could not legally be sold as food. Criminal distributors attempted to refine it, then marketed it in unmarked plastic containers as inexpensive olive oil.

Researchers conclusively identified the contaminated oil as the vehicle behind the outbreak, which became known as toxic oil syndrome. However, researchers have never definitively identified the exact chemical compound responsible for the disease. The oil contained a complex mixture of altered substances and contaminants rather than one easily isolated poison.

Approximately 20,000 people became ill, and several hundred died during the initial outbreak and ensuing years. Many survivors were left with lasting muscular, neurological, vascular, and immune-system problems from one of Europe’s worst modern food-poisoning disasters.^[8]

2 Yusho Disease

In 1968, doctors in western Japan began seeing patients with a strange collection of symptoms. Their skin and nails darkened, their eyelids swelled, and severe acne-like eruptions appeared across their bodies. Some also experienced numbness, fatigue, headaches, and eye and internal-organ problems.

The illness often struck several members of the same household, suggesting that the victims shared either an infection or an environmental exposure. Interviews eventually revealed that the affected families had consumed rice bran oil manufactured by the Kanemi Company.

During production, the oil was heated while a synthetic heat-transfer fluid circulated through nearby pipes. Leaks allowed polychlorinated biphenyls, or PCBs, to contaminate the edible oil. Heating also produced highly toxic related compounds, including polychlorinated dibenzofurans.

The resulting mass poisoning became known as Yusho, meaning “oil disease.” At least 1,900 people were officially identified as patients, although far more purchased or consumed oil from the affected batches.

Decades later, researchers continued to detect elevated concentrations of some contaminants in patients’ bodies. Survivors also continued experiencing chronic symptoms, turning what began as a baffling skin outbreak into a lifelong industrial-poisoning disaster.^[9]

1 Endemic Arsenicosis

During the 1970s and 1980s, millions of tube wells were installed across rural Bangladesh and neighboring parts of India. The wells were intended to provide families with cleaner drinking water than the ponds and rivers contaminated with disease-causing microorganisms. Instead, some of them created another public health catastrophe.

By the 1980s, doctors in West Bengal were encountering patients with unusual pigmentation and rough, thickened skin on their palms and soles. Prolonged exposure was also associated with ulcers, cardiovascular problems, nerve damage, and cancers of the skin and internal organs. Researchers officially detected similar contamination in Bangladesh in 1993.

Because symptoms developed gradually and varied widely, doctors and public health authorities did not immediately recognize that millions of seemingly separate medical problems shared one cause. Researchers eventually connected the illnesses to naturally occurring inorganic arsenic in the groundwater.

Industry did not place the arsenic there, and it was not introduced by the wells. It was already present in underground sediments and dissolved into the water drawn from certain aquifers. The millions of wells installed by the Bangladeshi government, private households, aid organizations, and international agencies had generally not been tested for the poison.

The campaign had successfully reduced exposure to pathogens in contaminated surface water, but it also exposed millions of people to arsenic for years. The World Health Organization has described the contamination of Bangladesh’s drinking water as the largest poisoning of a population in history.^[10]