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5 Deadliest Poisons Known to Man and Their Effects

John studies physics and knows a lot about deadly substances.

Learn all about five of the world's most dangerous poisons and their effects

Learn all about five of the world's most dangerous poisons and their effects

Whether you plan to use the following information to murder your ex-wife or to make the dog next door shut up once and for all, use it wisely. The following article contains information about the deadliest substances known to man, either inhaled or ingested.

5 Most Dangerous Poisons

  1. Botulinum Toxin or Botox
  2. Ricin
  3. Anthrax
  4. Sarin
  5. Tetrodotoxin

A poison is described by the Merriam-Webster dictionary as "a substance that through its chemical action usually kills, injures, or impairs an organism"—and the following five are the most dangerous found on earth.

A poison is only defined by the dosage. For example, even drinking too much water could kill a human (although it would have to be about two swimming pools worth). So, something is only officially defined as a poison when administered in a dose that causes harm or death.

Overview of Top 5 Deadly Poisons

The symptoms experienced will depend on the method of consumption. Some lethal dosage estimates are based on animal studies.

PoisonType of PoisonLethal DosageEffects

Botulinum Toxin or Botox

Neurotoxic protein produced by bacteria

~3000 U for a 70-kg adult (values based on animal studies)

Blurred vision, slurred speech, dry mouth, difficulty breathing and swallowing, muscle weakness


Carbohydrate-binding protein; toxin

2–30 castor oil plant seeds (ingested); 5–10 micrograms per kilogram (inhaled or injected)

Nausea, vomiting, abdominal pain, dehydration, cough, pulmonary edema, respiratory failure


Infection caused by bacteria

8,000–50,000 spores (inhaled); <10 spores (cutaneous exposure)

Fever, dizziness, cough, headache, body aches, fainting, flushing, swelling (for cutaneous and injected anthrax)


Synthetic compound; nerve agent

>0.01 milligrams per kilogram; rate of mortality depends on concentration of dose

Runny nose, blurred vision, cough, drooling, drowsiness, headache, vomiting, convulsions, respiratory failure, paralysis



2–3 milligrams

Numbness of lips and tongue, headache, vomiting, dizziness, seizures, respiratory arrest, paralysis

1. Botulinum Toxin or Botox

Type of Poison: Neurotoxic protein

Forms: Protein developed from bacteria

Methods of Exposure: Injection, ingestion of contaminated food, wound infection

Botulinum toxin is a protein produced by a bacterium called Clostridium botulinum and other related species. Where do they come up with these names? Anyway, this bacterium produces the botulinum toxin, which is a neurotoxin, meaning the toxin inhibits neuron control in the body.

The toxins produced by the bacteria are some of the most powerful neurotoxins known to man; however, you may have heard of them as "botox." But now you're wondering, "why didn't those injections my mother-in-law had a few months ago kill her, then?" Well, the doctors that perform botox surgery are highly skilled (granted you pick a proper one) who know just the right amount of Botulinum toxin to inject into the patient.

What the toxins do is attack the neurotransmitters responsible for triggering muscle contractions so the muscles cannot be released. This gets rid of the wrinkles in people's faces to some degree; however, it's not permanent and needs topping up every few months.

What Causes Botulism?

There are several causes of botulism⁠—foodborne botulism, wound botulism and infant botulism. Foodborne botulism is most commonly caused by eating from improperly canned foods that contain the toxin. In wound botulism, the toxin enters the body through an open wound. In infant botulism, bacteria is usually consumed by the infant, which then produces the toxin.

The bacterium usually grows on improperly handled or prepared meat products, and consumption can lead to paralysis, which in the worst cases can lead to death. In less severe cases, the ingestion of the toxins causes minor and temporary muscle paralysis.

Symptoms of Botulinum Toxin Exposure

  • Paralysis
  • Difficulty swallowing and dry mouth
  • Nausea and vomiting
  • Trouble breathing
  • Facial weakening
  • Blurred vision

Other Uses for Botulinum Toxin

Yes, botulinum toxin has medical uses as well. Due to its paralysis effects, it is used as a treatment for a number of disorders that result in muscle spasm and even for refractory overactive bladder. It's also used to prevent excessive sweating and chronic migraine headaches in addition to its uses in cosmetic surgery.

Castor beans from the Ricinus communis plant

Castor beans from the Ricinus communis plant

2. Ricin

Type of Poison: Naturally occurring protein

Forms: Powder, pellet, mist; can be dissolved in water or weak acid

Methods of Exposure: Ingestion of castor beans; exposure through food, air or water; subcutaneous injection of pellets

Ricin is a highly toxic protein that occurs naturally in the castor oil plant, Ricinus communis. Ricin is poisonous to humans if inhaled, injected or ingested, and a dose the size of a few grains of table salt can kill an adult human. Yikes! It's undoubtedly very dangerous, yet it is grown somewhat commonly in gardens in Britain.

Ricin prevents cells from combining amino acids it receives from the ribosomes of the cell, to create proteins. This is essential to all living cells, so without it, the consequences aren't too fabulous. The symptoms caused by lack of protein after receiving a dose of ricin can be severe diarrhea, and some victims can die of shock. Symptoms can take hours or even days to appear; however, death usually occurs after about 3–5 days of exposure.

Symptoms of Ricin Exposure

  • Respiratory distress
  • Fever
  • Cough
  • Nausea
  • Excessive sweating
  • Pulmonary edema
  • Vomiting
  • Diarrhea
  • Seizures

How Is Ricin Made?

The ricin itself comes from the inside of castor beans, produced by the plant. Ingestion of 5–20 of these can prove fatal for an adult. Ricin can also be made from the waste left over from the production of castor oil.

Ricin Mailed to U.S. Government Officials

In 2013, envelopes that tested positive for ricin and were addressed to several U.S. government officials, including President Barack Obama, were intercepted at a federal mail facility.

In 2018, ricin was discovered in envelopes addressed to several high-profile U.S. government officials, including President Donald Trump.

3. Anthrax

Type of Poison: Human and animal pathogen; bacterium

Form: Spores

Methods of Exposure: Cutaneous, inhalation, injection, oral consumption

Not to be confused with the thrash metal band from New York, Anthrax is an infectious disease caused by a bacterium called Bacillus anthracis. The bacterium can produce spores that are able to survive in extreme conditions, even in places such as Antarctica. (There was even a case where disturbed graves of animals caused reinfection after 70 years of the animal being dead.)

Symptoms of Anthrax Exposure

When these spores are inhaled, ingested or touched by a cut in the skin, they reactivate and multiply rapidly within the host. Anthrax poisoning symptoms start with a painless ulcer on the area of entry; however, that starts to get much worse. The lymph glands around the ulcer start to swell up, and the ulcer grows with a characteristic black dying area in the centre. Sufferers may also experience vomiting of blood, loss of appetite and inflammation of the intestinal tract. The throat and mouth can also develop lesions causing large amounts of pain. Other symptoms include:

  • Fever
  • Chills
  • Vomiting
  • Dizziness
  • Headache
  • Body aches
  • Fainting
  • Flushing
  • Abscesses (from injection)

Anthrax Treatment and Vaccine

If left untreated, anthrax leads to death. However, luckily there is a vaccine, created in 1881 by Louis Pasteur, a French scientist, and this has been further improved by scientists today.

Antibiotic treatment is effective if it's administered in the early stages of anthrax exposure.

Anthrax as a Bioweapon

There is evidence suggesting that the German army used anthrax in World War I to infect livestock provided to Allied Nations by neutral states. Over the next several decades, Japan, the U.S. and Britain experimented with anthrax as a bioweapon; although a post-WWI treaty prevented its use in biological warfare, it did not outlaw "research." In the 1950s, the U.S. expanded its bioweapons program, but by the 1960s, growing international concern about the stockpiling of bioweapons ultimately resulted in a 1970s treaty that resulted in the destruction of most of the U.S.'s bioweapons, including anthrax.

After the September 11, 2001, terrorist attacks in the U.S., envelopes containing anthrax spores were mailed to news media agencies and two U.S. senators' offices, resulting in a total of five deaths.

A Sarin chemical weapon

A Sarin chemical weapon

4. Sarin

Type of Poison: Synthetic compound

Form: Liquid; clear, odourless, colorless, tasteless

Methods of Exposure: Inhalation, absorption, eye contact, through food or drink

Sarin is a synthetic compound that is found as a clear, odourless liquid. It is an extremely powerful nerve agent, estimated at 500 times more toxic than cyanide, and has been used in chemical warfare, a famous example being the sarin gas attack on the Tokyo subway.

How Can I Be Exposed to Sarin?

The two main ways to be affected by sarin are via inhalation and absorption through the skin. Even at very low concentrations, sarin can be fatal, and even people who receive a nonlethal dose who are left untreated can suffer permanent neurological damage.

Symptoms of Sarin Exposure

  • Runny nose
  • Eye pain
  • Blurred vision
  • Drooling
  • Coughing
  • Diarrhea
  • Nausea and vomiting
  • Headache
  • Convulsions
  • Paralysis

Needless to say, sarin does not sound particularly pleasant, and what's worse is that any clothing that comes into contact with sarin vapour can still maintain that vapour for up to 30 minutes, meaning lots more people can inhale it.

Sarin as an Agent of Chemical Warfare

Sarin was first produced in Germany by scientists attempting to create a stronger pesticide; it is believed that up to 10 tonnes were produced in Nazi Germany. By the 1950s, NATO adopted sarin as a standard chemical weapon; however, since the 1993 U.N. Chemical Weapons Convention, more than 15,000 tonnes of sarin have been destroyed.

Sarin has been used in chemical attacks in Japan and the Middle East, killing at least 350 people and up to more than 1,700.

All nerve agents cause their toxic effects by preventing the proper operation of an enzyme that acts as the body’s “off switch” for glands and muscles. Without an “off switch,” the glands and muscles are constantly being stimulated. Exposed people may become tired and no longer be able to keep breathing. Sarin is the most volatile of the nerve agents. This means it can easily and quickly evaporate from a liquid into a vapor and spread into the environment.

— Centers for Disease Control and Prevention



5. Tetrodotoxin

Type of Poison: Neurotoxin

Forms: Colorless, crystalline solid

Methods of Exposure: Ingestion of fish or other food containing the neurotoxin

The things we put ourselves through for good food—well, that's if you consider the organs of a pufferfish to be good food. The tetrodotoxin or TTX is a potent neurotoxin to which there is no known antidote. It is commonly found in pufferfish but can also be found in some types of newt, toad, octopus, sea stars, angelfish and flatworm. It is used in the animals as a biotoxin to warn predators and keep them away, or as a venom in some octopi.

It is extremely toxic and can get into the human body by almost any means—ingestion, inhalation or through cuts in the skin. What the toxin does is block sodium channels in the body that are required for transmission of signals between the body and brain. Therefore, the symptoms of tetrodotoxin poison are paralysis of muscles, loss of sensation and loss of regular heart rate—meaning that, in most cases, around six hours after consumption, death will occur. However, some studies have shown that symptoms can take up to 20 hours to appear.

Symptoms of Tetrodotoxin Poisoning

  • Numbness and paresthesia of mouth and lips
  • Headache
  • Facial numbness
  • Salivation
  • Nausea and vomiting
  • Diarrhea
  • Paralysis
  • Low blood pressure
  • Seizures
  • Coma

The pufferfish containing the nasty toxin is a delicacy in Japan, and the toxin is not removed from the organs after cooking. Amazingly, people still put their neck on the line to try the fish. Up to five Japanese people die on average every year from eating poorly prepared pufferfish organs.

What Are Some Other Deadly Substances?

Carbon monoxide

Batrachotoxin (BTX)

Chlorine trifluoride









Belladonna or Deadly Nightshade

Well, there you have it! The top five deadliest poisons known to man. I hope this hasn't worried you too much; there are antidotes for many of them, and some in development for the ones that don't have one yet. It's amazing to think that things as simple as plants can produce such powerful poisons that they could easily kill us. It just goes to show that man is not invincible.

Works Cited

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.


Kevin Onyango on February 25, 2019:


Gamer on January 24, 2019:

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Abdi hashi on January 07, 2019:

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sadab saman on September 10, 2017:

that is so cool