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Symptoms and Signs of Cyanide Poisoning

Doctor's Notes on Cyanide Poisoning

Cyanide is a potentially deadly poison that makes the human body’s cells unable to use oxygen. Signs and symptoms may be difficult to relate to the poison; for example, weakness, confusion, unusual behavior, shortness of breath, sleepiness, headache, vomiting, abdominal pain, abnormal heartbeats, coma, seizures and death. Chronic cyanide poisoning can occur over a long time periods with gradual onset of symptoms and signs. Acute cyanide poisoning has a rapid onset of almost immediate sudden collapse and may exhibit seizures and a coma before death. Other subtle signs are an unusual pink or cherry-red coloration of the skin and the breath may smell like bitter almonds.

Accidental or intentional exposure to cyanide or compounds that contain cyanide is the cause of cyanide poisoning. Accidental exposures to the poison include fires, especially those that burn rubber, plastic and silk - they can produce cyanide fumes. Industrial exposures to cyanide occur in chemical research labs, photography labs, plastic, fiber and metal processing plants. Potassium cyanide is used in metal extraction plants and to make chemicals such as insecticides. Cigarette smoke is the most common source of cyanide exposure for most people. Some plants, especially seed pits from plants like apricot, bitter almonds, peaches, pears and apples, contain cyanide containing glycosides that can cause poisoning if the seed pits are ingested in large amounts. Laetrile, a cancer treating drug from Mexico not approved for use by the FDA, has the side effect of potential cyanide poisoning. Although most chemicals like solvents, plastics and others containing cyanide compounds have been taken off the market, some may still be available.

Intentional exposure to cyanide usually happens when a person wants to commit suicide or wants to harm or kill someone. Intentional exposures to cyanide-containing pills or tablets can cause a rapid and painful death. However, small amounts of cyanide placed in foods also can be deadly over time.

Medical Author:
Medically Reviewed on 3/11/2019

Cyanide Poisoning Symptoms

Detection of cyanide poisoning can be difficult. The effects of cyanide ingestion are very similar to the effects of suffocation. The mechanism of toxicity occurs because cyanide stops the cells of the body from being able to use oxygen, which all cells need to survive.

  • The symptoms of cyanide poisoning are similar to those experienced when hiking or climbing at high altitudes, and include:
  • Typically, acute cyanide ingestion will have a dramatic, rapid onset, immediately affecting the heart and causing sudden collapse. It also can immediately affect the brain and cause a seizure or coma.
  • Chronic cyanide poisoning (over a long period of time) from ingestion or environmental poisoning will have a more gradual onset, and symptoms may include:
  • The skin of a cyanide-poisoned person can sometimes be unusually pink or cherry-red because oxygen will stay in the blood and not get into the cells. The person may also breathe very fast and have either a very fast or very slow heartbeat. Sometimes the person's breath can smell like bitter almonds, though this can be difficult to detect.
  • Perhaps most important is the environment, rather than the signs or symptoms.
    • A person who works in a laboratory or plastics factory has a higher risk of cyanide poisoning.
    • Home, RV, boat, or building fires always include the additional concern of cyanide exposure.
    • If you know someone has been depressed or has substance abuse problems and you find him or her with any of the signs or symptoms of cyanide poisoning, then a suicide attempt is possible.

Cyanide Poisoning Causes

Common sources of cyanide poisoning include:

  • Fires: Smoke inhalation during the burning of common substances such as rubber, plastic, and silk can create cyanide fumes and cause cyanide poisoning.
  • Photography, chemical research, synthetic plastics and fibers, metal processing, fumigation and pesticides, mining, and electroplating industries use hydrogen cyanide. Potassium cyanide is used in gold and silver extraction, chemical analysis, to make other chemicals, and as an insecticide.
  • Plants: Mostly from the family Rosaceae, seeds and pits from plants such as apricot, bitter almond, cherry laurel, plum, peach, pear, and apple contain cyanogenic glycosides. A type of potato called cassava can also cause cyanide poisoning. Fortunately, only chronic or massive ingestion of any of these plants or pits can cause serious cyanide poisoning.
  • Laetrile, a compound that contains amygdalin (a chemical found in the pits of raw fruits, nuts, and plants) has been purported as a cancer treatment worldwide. One of the side effects of laetrile is cyanide poisoning. The Food and Drug Administration (FDA) has not approved laetrile as a cancer treatment in the United States. The drug is also made and used as a cancer treatment in Mexico under the name "laetrile/amygdalin."
  • Certain chemicals, after ingestion, can be converted by the body into cyanide and cause cyanide poisoning. Most of these chemicals have been removed from the market, but some old artificial nail polish removers, solvents, and plastics manufacturing solutions can contain these substances.
  • Cigarette smoke is the most common source of cyanide exposure for most people. Cyanide is naturally found in tobacco, and smokers can have more than 2.5 times the mean whole blood cyanide level of nonsmokers, though this is generally not enough to cause poisoning.

Those most at risk of cyanide poisoning are those who work in industries that use this chemical and people who intentionally try to kill themselves. Those who attempt suicide by using cyanide pills or capsules may believe it is a quick and painless death, however, cyanide burns the stomach and prevents the body from using oxygen, causing a painful death.

For most people, cyanide only causes poisoning if a fire occurs or if some of the compounds mentioned above are accidentally ingested.

Uncommon and Common Food-Poisoning Dangers in Pictures Slideshow

Uncommon and Common Food-Poisoning Dangers in Pictures Slideshow

Listeria bacteria can contaminate fresh produce, like cantaloupes, as well as some processed foods, like cheeses. Symptoms of infection include fever, muscle aches, upset stomach, or diarrhea -- occurring 2 days to 2 months after exposure.

Safety: Scrub raw produce and dry before cutting. Store in fridge below 40 F. Clean everything in contact with a whole melon.


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.