In Chinese alchemy, elixir poisoning refers to the toxic effects from elixirs of immortality that contained metals and minerals such as mercury and arsenic. The official "Twenty-Four Histories" record numerous Chinese emperors, nobles, and officials who ironically died from taking elixirs in order to prolong their lifespans. The first emperor to die from elixir poisoning was likely Qin Shi Huang (d. 210 BCE) and the last was Yongzheng (d. 1735). Despite common knowledge that immortality potions could be deadly, fangshi and Daoist alchemists continued the elixir-making practice for two millennia.

Zhu Ling (, born 1973) is best known as the victim of an unsolved 1995 thallium poisoning case in Beijing, China. Her symptoms were posted to the Internet via a Usenet newsgroup by her friend from Peking University, Bei Zhicheng and were subsequently proven to be caused by thallium poisoning. Her case was then reviewed by physicians in many different countries who examined her symptoms and made suggestions as to diagnoses and treatment. This effort was recognized as the first large scale tele-medicine trial. Her life was ultimately saved, but she suffered serious neurological damage and permanent physical impairment.

This case drew great attention in the Chinese media, because the victim and the suspect were living in the same dormitory in the most prestigious university of China, and the case was never solved. Internet discussion of the crime has continued since then and became a hot topic on major online Chinese communities very frequently as a high-profile cold case.

Convulsive symptoms include painful seizures and spasms, diarrhea, paresthesias, itching, mental effects including mania or psychosis, headaches, nausea and vomiting. Usually the gastrointestinal effects precede central nervous system effects.

Tetraphobia (from Greek τετράς—"tetras", "four" and φόβος—"phobos", "fear") is the practice of avoiding instances of the number . It is a superstition most common in East Asian nations.

The symptoms can be roughly divided into convulsive symptoms and gangrenous symptoms.

The etymology of English elixir derives from Medieval Latin "", from Arabic ("al-ʾiksīr"), probably from Ancient Greek ("xḗrion" "a desiccative powder for wounds"). "Elixir" originated in medieval European alchemy meaning "A preparation by the use of which it was sought to change metals into gold" (elixir stone or philosopher's stone) or "A supposed drug or essence with the property of indefinitely prolonging life" (elixir of life). The word was figuratively extended to mean "A sovereign remedy for disease. Hence adopted as a name for quack medicines" (e.g., Daffy's Elixir) and "The quintessence or soul of a thing; its kernel or secret principle". In modern usage, "elixir" is a pharmaceutical term for "A sweetened aromatic solution of alcohol and water, serving as a vehicle for medicine" ("Oxford English Dictionary", 2nd ed., 2009). Outside of Chinese cultural contexts, English "elixir poisoning" usually refers to accidental contamination, such as the 1937 Elixir sulfanilamide mass poisoning in the United States.

"Dān" 丹 "cinnabar; vermillion; elixir; alchemy" is the keyword for Chinese immortality elixirs. The red mineral cinnabar ("dānshā" 丹砂 lit. "cinnabar sand") was anciently used to produce the pigment vermilion ("zhūhóng" 朱紅) and the element mercury ("shuǐyín" 水銀 "watery silver" or "gǒng" 汞).

According to the "ABC Etymological Dictionary of Old Chinese", the etymology of Modern Standard Chinese "dān" from Old Chinese "*tān" (< *"tlan" ?) 丹 "red; vermillion; cinnabar", "gān" 矸 in "dāngān" 丹矸 from *"tân-kân" (< *"tlan-klan" ?) "cinnabar; vermillion ore", and "zhān" from *"tan" 旃 "a red flag" derive from Proto-Kam-Sui *"h-lan" "red" or Proto-Sino-Tibetan *"tja-n" or *"tya-n" "red". The *"t-" initial and *"t-" or *"k-" doublets indicate that Old Chinese borrowed this item. (Schuessler 2007: 204).

Although the word "dan" 丹 "cinnabar; red" frequently occurs in oracle script from the late Shang Dynasty (ca. 1600-1046 BCE) and bronzeware script and seal script from the Zhou Dynasty (1045-256 BCE), paleographers disagree about the graphic origins of the logograph 丹 and its ancient variants 𠁿 and 𠕑. Early scripts combine a 丶 dot or ⼀ stroke (depicting a piece of cinnabar) in the middle of a surrounding frame, which is said to represent:

- "jǐng" 井 "well" represents the mine from which the cinnabar is taken" ("Shuowen Jiezi")

- "the crucible of the Taoist alchemists" (Léon Wieger )

- "the contents of a square receptacle" (Bernhard Karlgren)

- "placed in a tray or palette to be used as red pigment" (Wang Hongyuan 王宏源)

- "mineral powder on a stretched filter-cloth" (Needham and Lu).

Many Chinese elixir names are compounds of "dan", such as "jīndān" 金丹 (with "gold") meaning "golden elixir; elixir of immortality; potable gold" and "xiāndān" 仙丹 (with "Daoist immortal") "elixir of immortality; panacea", and "shéndān" 神丹 (with "spirit; god") "divine elixir". "Bùsǐ zhī yào" 不死之藥 "drug of deathlessness" was another early name for the elixir of immortality. Chinese alchemists would "liàndān" 煉丹 (with "smelt; refine") "concoct pills of immortality" using a "dāndǐng" 丹鼎 (with "tripod cooking vessel; cauldron") "furnace for concocting pills of immortality". In addition, the ancient Chinese believed that other substances provided longevity and immortality, notably the "língzhī" 靈芝 ""Ganoderma" mushroom".

The transformation from chemistry-based "waidan" 外丹 "external elixir/alchemy" to physiology-based "neidan" 內丹 "internal elixir/alchemy" gave new analogous meanings to old terms. The human body metaphorically becomes a "ding" "cauldron" in which the adept forges the Three Treasures (essence, life-force, and spirit) within the "jindan" Golden Elixir within the "dāntián" 丹田 (with "field") "lower part of the abdomen".

In early China, alchemists and pharmacists were one in the same. Traditional Chinese Medicine also used less concentrated cinnabar and mercury preparations, and "dan" means "pill; medicine" in general, for example, "dānfāng" 丹方 semantically changed from "prescription for elixir of immortality" to "medical prescription". "Dan" was lexicalized into medical terms such as " dānjì" 丹劑 "pill preparation" and "dānyào" 丹藥 "pill medicine".

The Chinese names for immortality elixirs have parallels in other cultures and languages, for example, Indo-Iranian "soma" or "haoma", Sanskrit "amrita", and Greek "ambrosia".

The 1951 Pont-Saint-Esprit mass poisoning, also known as Le Pain Maudit, occurred on 15 August 1951, in the small town of Pont-Saint-Esprit in southern France. More than 250 people were involved, including 50 persons interned in asylums and resulted in 7 deaths. A foodborne illness was suspected, and among these it was originally believed to be a case of "cursed bread" ("pain maudit").

Most academic sources accept ergot poisoning as the cause of the epidemic, while a few theorize other causes such as poisoning by mercury, mycotoxins, or nitrogen trichloride.

Acute mercury exposure has given rise to psychotic reactions such as delirium, hallucinations, and suicidal tendency. Occupational exposure has resulted in erethism, with irritability, excitability, excessive shyness, and insomnia as the principal features of a broad-ranging functional disturbance. With continuing exposure, a fine tremor develops, initially involving the hands and later spreading to the eyelids, lips, and tongue, causing violent muscular spasms in the most severe cases. The tremor is reflected in the handwriting which has a characteristic appearance. In milder cases, erethism and tremor regress slowly over a period of years following removal from exposure. Decreased nerve conduction velocity in mercury-exposed workers has been demonstrated. Long-term, low-level exposure has been found to be associated with less pronounced symptoms of erethism, characterized by fatigue, irritability, loss of memory, vivid dreams, and depression (WHO, 1976).

Effects of chronic occupational exposure to mercury, such as that commonly experienced by affected hatters, include mental confusion, emotional disturbances, and muscular weakness. Severe neurological damage and kidney damage can also occur. Neurological effects include Korsakoff's dementia and erethism (the set of neurological symptoms characteristically associated with mercury poisoning). Signs and symptoms can include red fingers, red toes, red cheeks, sweating, loss of hearing, bleeding from the ears and mouth, loss of appendages such as teeth, hair, and nails, lack of coordination, poor memory, shyness, insomnia, nervousness, tremors, and dizziness. A survey of exposed U.S. hatters revealed predominantly neurological symptomatology, including intention tremor. After chronic exposure to the mercury vapours, hatters tended to develop characteristic psychological traits, such as pathological shyness and marked irritability (box). Such manifestations among hatters prompted several popular names for erethism, including "mad hatter disease", "mad hatter syndrome", "hatter's shakes" and "Danbury shakes".

Chang (; ) and Eng (; ) Bunker (May 11, 1811 – January 17, 1874) were Thai-American conjoined twin brothers whose condition and birthplace became the basis for the term "Siamese twins".

Foot binding was the custom of applying tight binding to the feet of young girls to modify the shape of their feet. The practice possibly originated among upper class court dancers during the Five Dynasties and Ten Kingdoms period in 10th century China, then became popular among the elite during the Song dynasty and eventually spread to all social classes by the Qing dynasty. Foot binding became popular as a means of displaying status (women from wealthy families, who did not need their feet to work, could afford to have them bound) and was correspondingly adopted as a symbol of beauty in Chinese culture. Foot binding limited the mobility of women, resulting in them walking in a swaying unsteady gait, although some women with bound feet working outdoor had also been reported. The prevalence and practice of foot binding varied in different parts of the country. Feet altered by binding were called lotus feet.

It has been estimated that by the 19th century, 40–50% of all Chinese women may have had bound feet, and up to almost 100% among upper class Han Chinese women. The Manchu Kangxi Emperor tried to ban foot binding in 1664 but failed. In the later part of the 19th century, Chinese reformers challenged the practice but it was not until the early 20th century that foot binding began to die out as a result of anti-foot-binding campaigns. Foot-binding resulted in lifelong disabilities for most of its subjects, and a few elderly Chinese women still survive today with disabilities related to their bound feet.

Anti-Chinese sentiment in Japan has been present since the Tokugawa period. Anti-Chinese sentiments in Japan have been on a sharp rise since 2002. According to Pew Global Attitude Project (2008), unfavorable view of China was 84%, unfavorable view of Chinese people was 73%.

The 1971 Iraq poison grain disaster was a mass methylmercury poisoning incident that began in late 1971. Grain treated with a methylmercury fungicide and never intended for human consumption was imported into Iraq as seed grain from Mexico and the United States. Due to a number of factors, including foreign-language labelling and late distribution within the growing cycle, this toxic grain was consumed as food by Iraqi residents in rural areas. People suffered from paresthesia (numbness of skin), ataxia (lack of coordination of muscle movements) and vision loss, symptoms similar to those seen when Minamata disease affected Japan. The recorded death toll was 459 people, but figures at least ten times greater have been suggested. The 1971 poisoning was the largest mercury poisoning disaster when it occurred, with cases peaking in January and February 1972 and stopping by the end of March.

Reports after the disaster recommended tighter regulation, better labelling and handling of mercury-treated grain, and wider involvement of the World Health Organization in monitoring and preventing poisoning incidents. Investigation confirmed the particular danger posed to fetuses and young children.

Hallmark symptoms of ciguatera in humans include gastrointestinal, cardiovascular, and neurological effects. Gastrointestinal symptoms include nausea, vomiting, and diarrhea, usually followed by neurological symptoms such as headaches, muscle aches, paresthesia, numbness of extremities, mouth and lips, reversal of hot and cold sensation, ataxia, vertigo, and hallucinations. Severe cases of ciguatera can also result in cold allodynia, which is a burning sensation on contact with cold. Neurological symptoms can persist and ciguatera poisoning is occasionally misdiagnosed as multiple sclerosis. Cardiovascular symptoms include bradycardia, tachycardia, hypotension, hypertension, orthostatic tachycardia, exercise intolerance, and rhythm disorders. Death from the condition can occur, but is extremely rare.

Dyspareunia and other ciguatera symptoms have developed in otherwise healthy males and females following sexual intercourse with partners suffering ciguatera poisoning, signifying that the toxin may be sexually transmitted. Diarrhea and facial rashes have been reported in breastfed infants of poisoned mothers, suggesting that ciguatera toxins migrate into breast milk.

The symptoms can last from weeks to years, and in extreme cases as long as 20 years, often leading to long-term disability. Most people do recover slowly over time. Often patients recover, but symptoms then reappear. Such relapses can be triggered by consumption of nuts, seeds, alcoholic beverages, fish or fish-containing products, chicken or eggs, high histamine foods, temperature extremes, or by exposure to fumes such as those of bleach and other chemicals. Exercise is also a possible trigger.

Symptoms include:

- Dizziness

- Backache

- Tiredness

- Weakness

- Insomnia

- Frequent dreams

- Sexual dysfunctions; premature ejaculation or impotence.

Yunnan sudden death syndrome is a label used to define unexplained cases of cardiac arrest, which afflicted significant numbers of rural villagers in Yunnan province, in southwest China. Cases occurred almost always during the midsummer rainy season (from June to August), at an altitude of . The cause turned out to be a mushroom now blamed for an estimated 400 deaths in the past three decades.

The mysterious fatalities were recorded for decades before researchers from the Chinese Center for Disease Control and Prevention isolated a significant factor common in every case: a tiny unknown mushroom which was unintentionally gathered and consumed during wild mushroom harvests in the region. Previously the syndrome was thought to be caused by Keshan disease, caused by the Coxsackie virus.

The mushroom, "Trogia venenata", is also known as 'Little White'. It has been determined that families collecting fungi to sell have been eating these Little White mushrooms as they have no commercial value. Three amino acids present in the mushrooms have been shown to be toxic. The mushrooms have also been shown to contain very high quantities of barium, and it may be that some of the deaths are simply from barium poisoning.

In the hours before death, about two-thirds of the victims had such symptoms as nausea, dizziness, heart palpitations, seizures and fatigue.

However, in December 2012 it was announced that Dr Xu Jianping (徐建平) has been collecting samples of "Trogia venenata" in Yunnan for the past three years, and his research now shows that barium levels in the wild mushroom are no higher than those of common foods such as poultry and fish. Nonetheless, it appears the mushroom will still likely play a role. Since publication of the widely circulated 2010 "Science" article, no instances of Yunnan sudden death syndrome have been reported.

Erethism or erethism mercurialis is a neurological disorder which affects the whole central nervous system, as well as a symptom complex derived from mercury poisoning. This is also sometimes known as the mad hatter disease. Historically, this was common among old England felt-hatmakers who used mercury to stabilize the wool in a process called felting, where hair was cut from a pelt of an animal such as a rabbit. The industrial workers were exposed to the mercury vapors, giving rise to the expression “mad as a hatter.” Some believe that the character the Mad Hatter in Lewis Carroll's Alice in Wonderland is an example of someone suffering from erethism, but the origin of this account is unclear. The character was almost certainly based on Theophilus Carter, an eccentric furniture dealer who was well known to Carroll.

Mad hatter disease, or mad hatter syndrome, was an occupational disease among hatmakers, caused by chronic mercury poisoning. It affected those whose felting work involved prolonged exposure to mercury vapors. The neurotoxic effects included tremor and the pathological shyness and irritability characteristic of erethism.

Erethism is due to mercury poisoning. Mercury is an element that is found all over the earth in soil, rocks, and water. People who get erethism are usually exposed to jobs that have something to do with these elements, such as construction. People who work in factory jobs tend to have a higher chance of getting erethism. The problem with mercury is that if humans are exposed to any of the forms of mercury, depending on the amount (dose), route (ingestion, skin contact, inhalation), duration (time) of exposure, it can be toxic. Some elemental and chemical forms of mercury (vapor, methylmercury, inorganic mercury) are more toxic than other forms. The human fetus and medically compromised people (for example, patients with lung or kidney problems) are the most susceptible to the toxic effects of mercury.

It is commonly characterized through behavioral changes such as irritability, low self-confidence, depression, apathy, shyness and timidity, and in some extreme cases with prolonged exposure to mercury vapors, delirium, personality changes and memory loss occur as a result. People with erethism find it difficult to interact socially with others, with behaviors similar to that of a social phobia. Although most of the effects of erethism are neurological, some physical problems arise as well, including a decrease in physical strength, “headaches, general pain, and tremors after exposure to metallic mercury” as well as irregular heartbeat. It has been documented that “the tremor in the hands can be so severe that the victim is unable to hold a glass of water without spilling its contents.”

The primary risk factor for erethism is long-term exposure to mercury vapors and gasses at high levels. One group at risk for mercury poisoning is industrial workers and those exposed to high levels of mercury residing naturally in the environment. Erethism is not as serious an issue as it was back before acceptable working condition regulations were enforced. Preventing mercury levels from getting too high limits the amount available for inhalation.

There is a risk of mercury poisoning in the home in some cases. Exposure to mercury vapor may stem from cultural and religious reasons where mercury is sprinkled on the floor of a home or car, burned in a candle, or mixed with perfume. Due to widespread use and popular concern, the risk of toxicity from dental amalgam has been exhaustively investigated. Many studies have not revealed convincing evidence of toxicity . However, in 2015 research showed that an increased mercury release from dental amalgam restorations after exposure to electromagnetic fields is a potential hazard for hypersensitive people and pregnant women.

Koro is a culture-specific syndrome delusional disorder in which an individual has an overpowering belief that one's genitalia are retracting and will disappear, despite the lack of any true longstanding changes to the genitals. Koro is also known as shrinking penis, and it is listed in the "Diagnostic and Statistical Manual of Mental Disorders". The syndrome occurs worldwide, and mass hysteria of genital-shrinkage anxiety has a history in Africa, Asia, and Europe. In the United States and Europe, the syndrome is commonly known as genital retraction syndrome. The condition can be diagnosed through psychological assessment along with physical examination to rule out genuine disorders of the genitalia that could be causing true retraction.

Most patients report acute anxiety attacks due to perceived genital retraction and/or genital shrinkage, despite a lack of any objectively visible biological changes in the genitalia that are longstanding. "Longstanding" refers to changes that are sustained over a significant period and do not appear reversible, unlike the effect of cold temperatures on some genital regions that cause retraction. These changes may trigger a koro attack when observed, although the effects of cold temperatures are objectively reversible. According to literature, episodes usually last several hours, though the duration may be as long as two days. There are cases in which koro symptoms persist for years in a chronic state, indicating a potential co-morbidity with body dysmorphic disorder. In addition to retraction, other symptoms include a perception of alteration of penis shape and loss of penile muscle tone. In cases when sufferers have no perception of retraction, some patients may complain of genital paraesthesia or genital shortening. Among females, the cardinal symptom is nipple retraction in the breast, generally into the breast as a whole.

Psychological components of koro anxiety include fear of impending death, penile dissolution and loss of sexual power. Feelings of impending death along with retraction and perceived spermatorrhea has a strong cultural link with Chinese traditional beliefs. This is demonstrated by the fact that Asians generally believe koro symptoms are fatal, unlike most patients in the West. Other ideational themes are intra-abdominal organ shrinkage, sex change to female or eunuch, non-specific physical danger, urinary obstruction, sterility, impending madness, spirit possession and a feeling of being bewitched.

Extremely anxious sufferers and their family members may resort to physical methods to prevent the believed retraction of the penis. A man may perform manual or mechanical penile traction, or "anchoring" by a loop of string or some clamping device. Similarly, a woman may be seen grabbing her own breast, pulling her nipple, or even having iron pins inserted into the nipple. Physical injury may occur from these attempts. These forceful attempts often lead to injuries, even death.

Devon colic was a condition that affected people in the English county of Devon during parts of the 17th and 18th centuries, before it was discovered to be lead poisoning.

The first written account of the colic comes from 1655. Symptoms began with severe abdominal pains and the condition was occasionally fatal. Cider is the traditional drink of Devonians, and the connection between the colic and cider drinking had been observed for many years. The condition was commonly attributed to the acidity of the beverage.

William Musgrave's publication "De arthritide symptomatica" (2nd edn, 1715) included the first scientific description of "Devonshire colic" – it was later referred to by John Huxham and Sir George Baker.

However, the precise cause was not discovered until the 1760s when Dr George Baker put forward the hypothesis that poisoning from lead in cider was to blame. He observed that the symptoms of the colic were similar to those of lead poisoning. He pointed out that lead was used in the cider making process both as a component of the cider presses and in the form of lead shot which was used to clean them. He also conducted chemical tests to demonstrate the presence of lead in Devon apple juice.

The publication of his results met with some hostile reaction from cider manufacturers, keen to defend their product. Once Baker's conclusions became accepted and the elimination of lead from the cider presses was undertaken, the colic declined. By 1818, Baker's son reported that it was "hardly known to exist" in Devon.

Shenkui is a culture bound syndrome native to China in which the individual suffers somatic symptoms with anxiety, believed to be caused by a loss of semen. And in Traditional Chinese Medicine, shen (kidney) is the reservoir of vital essence in semen (ching) and k’uei signifies deficiency. In simplified Chinese it is called 肾亏, Traditional Chinese 腎虧, and in pinyin Shènkuī.

Shenkui or shen-k'uei is one of several Chinese culture-bound syndromes locally ascribed to loss (or fear of loss) of Yang (Chinese: 陽) . In Traditional Chinese Medicine, Shenkui is believed to result from a deficiency in yang, obtained through the loss of semen. Semen is believed to be "lost" through excessive sexual activity or masturbation, nocturnal emissions, "white urine" which is believed to contain semen, or other mechanisms. Symptoms within the Chinese diagnostic system include dizziness, backache, tiredness, weakness, insomnia, frequent dreams, and complaints of sexual dysfunction (such as premature ejaculation or impotence). From an ethnopsychiatric perspective, additional symptoms are preoccupation with sexual performance, potential semen loss, and bodily complaints which may be taken as symptoms of lost yang.

Losing semen reduces Yang, causing an unbalance in the body. Nocturnal emissions, too much intercourse, and masturbation resulting in ejaculation lower the levels of semen, causing loss of Yang. Somatic symptoms may include body soreness, aches, lack of energy, fatigue, and possibly problems in sexual performance.

A person suffering form Shenkui may endure body aches, dizziness, tiredness, inability to sleep, and sexual dysfunction, all for which no physical cause can explain.

The passing of semen too often is avoided because it is believed to be crucial to a person’s health and safety. It is believed to be life-threatening if too much semen is lost.

"Chinese martial artists that remained celibate through years and years of extensive training were believed to be most powerful, therefore maintaining the power of one’s vital essence."

One of the main effects of cadmium poisoning is weak and brittle bones. Spinal and leg pain is common, and a waddling gait often develops due to bone deformities caused by the cadmium. The pain eventually becomes debilitating, with fractures becoming more common as the bone weakens. Other complications include coughing, anemia, and kidney failure, leading to death.

A marked prevalence in older, postmenopausal women has been observed. The cause of this phenomenon is not fully understood, and is currently under investigation. Current research has pointed to general malnourishment, as well as poor calcium metabolism relating to the women's age.

Recent animal studies have shown that cadmium poisoning alone is not enough to elicit all of the symptoms of itai-itai disease. These studies are pointing to damage of the mitochondria of kidney cells by cadmium as a key factor of the disease.

Ciguatera is a foodborne illness caused by eating certain reef fish whose flesh is contaminated with a toxin made by dinoflagellates such as "Gambierdiscus toxicus" which live in tropical and subtropical waters. These dinoflagellates adhere to coral, algae and seaweed, where they are eaten by herbivorous fish which in turn are eaten by larger carnivorous fish like barracudas, shark, and even omnivorous fish like basses and other fish like mullet. This is called biomagnification. Affected fish may show no sign of infection or, in more advanced cases, will be weakened and visibly thin, with yellowish eyes. As well, fish may be pale or a different color than usual.

"Gambierdiscus toxicus" is the primary dinoflagellate responsible for the production of a number of similar polyether toxins, including ciguatoxin, maitotoxin, gambieric acid and scaritoxin, as well as the long-chain alcohol palytoxin. Other dinoflagellates that may cause ciguatera include "Prorocentrum" spp., "Ostreopsis" spp., "Coolia monotis", "Thecadinium" spp. and "Amphidinium carterae". Predator species near the top of the food chain in tropical and subtropical waters are most likely to cause ciguatera poisoning, although many other species cause occasional outbreaks of toxicity.

Ciguatoxin is odourless, tasteless and cannot be removed by conventional cooking.

Researchers such as Ross M. Brown with his "New Religion" theory suggest that ciguatera outbreaks caused by warm climatic conditions in part propelled the migratory voyages of Polynesians between 1000 and 1400AD.

In 2017 an updated review of "Clinical, Epidemiological, Environmental, and Public Health Management" was published and is available at the National Institute of Health website.

Thallium and its compounds are often highly toxic. Contact with skin is dangerous, and adequate ventilation should be provided when melting this metal. Many thallium(I) compounds are highly soluble in water and are readily absorbed through the skin. Exposure to them should not exceed 0.1 mg per m of skin in an 8-hour time-weighted average (40-hour work week). Thallium is a suspected human carcinogen.

Part of the reason for thallium's high toxicity is that, when present in aqueous solution as the univalent thallium(I) ion (Tl), it exhibits some similarities with essential alkali metal cations, particularly potassium (due to similar ionic radii). It can thus enter the body via potassium uptake pathways. Other aspects of thallium's chemistry differ strongly from that of the alkali metals, such as its high affinity for sulfur ligands. Thus, this substitution disrupts many cellular processes (for instance, thallium may attack sulfur-containing proteins such as cysteine residues and ferredoxins). Thallium's toxicity has led to its use (now discontinued in many countries) as a rat and ant poison.

Among the distinctive effects of thallium poisoning are hair loss (which led to its initial use as a depilatory before its toxicity was properly appreciated) and damage to peripheral nerves (victims may experience a sensation of walking on hot coals), although the loss of hair only generally occurs in low doses; in high doses the thallium kills before this can take effect. Thallium was once an effective murder weapon before its effects became understood and an antidote (Prussian blue) discovered. Indeed, thallium poisoning has been called the "poisoner's poison" since thallium is colorless, odorless and tasteless; its slow-acting, painful and wide-ranging symptoms are often suggestive of a host of other illnesses and conditions.

After ingestion, toxic features usually develop within a few minutes. The major lethal consequence of aluminium phosphide ingestion is profound circulatory collapse, and is reportedly secondary to these toxins generated, which lead due to direct effects on cardiomyocytes, fluid loss, and adrenal gland damage. The signs and symptoms are non-specific, dose dependent and evolve with time passing. The dominant clinical feature is severe hypotension refractory to dopamine therapy. Other features may include dizziness, fatigue, tightness in the chest, headache, nausea, vomiting, diarrhoea, ataxia, numbness, paraesthesia, tremor, muscle weakness, diplopia and jaundice. If severe inhalation occurs, the patient may develop acute respiratory distress syndrome (ARDS), heart failure, arrhythmias, convulsion and coma. Late manifestation include liver and kidney toxicities.

The diagnosis of AAlP usually depends on the clinical suspicion or history (self-report or by attendants). In some nations, tablets of AlP are also referred to as "rice tablets" and, if there is a history of rice tablet ingestion, then it should be treated differently from other types of rice tablets that are made up of herbal products. For a silver nitrate test on gastric aspirate, diluted gastric content can be positive.

Acute aluminium phosphide poisoning (AAlPP) is a large, though under-reported, problem throughout the world, particularly in the Indian subcontinent. Aluminium phosphide (AlP), which is readily available as a fumigant for stored cereal grains, sold under various brand names such as "QuickPhos" and "Celphos", is highly toxic, especially when consumed from a freshly opened container. Death results from profound shock, myocarditis and multi-organ failure. Aluminium phosphide has a fatal dose of between . It has been reported to be the most common cause of suicidal death in North India. Deaths have also been reported in Iran. In January 2017, four children died at a trailer park in Amarillo, Texas, after the pesticide was used under the home to kill rats. Several incidents of death in travelers in Thailand and other parts of Southeast Asia may have been caused by aluminum phosphide or chlorpyrifos, an organophosphate insecticide, used in an attempt to kill bedbugs in hotels. Wired magazine reported on the problem in March 2014. A short film in Arabic on Youtube that focused on the problem in Saudi Arabia had over 3.5 million hits in 2014. The CDC has classified phosphine as immediately dangerous to life at 50 parts per million.