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A nice listing of poisons and their symptoms and signs. This is by no means exhaustive. Note that, in real life, most poisoning cases are accident or suicide rather than murder. It's not very good as a murder weapon as labs can always detect it in the body. However, sometimes poisoning deaths look like natural deaths, unless a toxicological analysis in done.

Please note that this is intended for fiction use only, not for medical use.

A useful website is the "Bad Bug Book by the Center for Food Safetly and Nutrition, which describes various food-poisoning agents, from bacteria, to toxins (bacterial, fungal, plant, combination), and others, often with links for more info.

Important note: This whole section has been compiled from books and websites, with occasional help from people working in this field. Like the rest of Deep Background (of which this is only a small part), this information is designed for writers of X-Files fiction, and covers only those things that they might be expected to need. It is not a comprehensive guide to the subject.


  • Carbon monoxide Odorless and colorless. Non-irritating. Found in car exhausts. It is cumulative - repeated small doses can build up over time. It kills by preventing the blood from carrying oxygen. Symptoms: Initially, dizziness and headaches when exerting yourself, then when at rest too. A higher dose affects coordination and makes the heart throb. Then comes collapse and death. Often the victim is unaware and just drifts slowly to sleep. Post-mortem appearance: Pinky skin. Cherry-red blood. Blood is fluid and doesn't want to clot. Lungs congested and the upper air passages contain a frothy fliud. Carbon monoxide remains in the blood for up to six months after death.



  • Hydrochloric As with most acids, not usually used to kill someone, but can be used to dispose of the corpse afterwards. Corrosive and colorless.

  • Nitric Usually colorless, though goes brown when oxidized.

  • SulphuricColorless. A dehydrating agent that extracts water from the body. Is strong enough to eat through bones as well as flesh. This process takes about 4 hours.


  • Potassium hydroxide (Caustic potash) Very corrosive. If consumed, it burns then mouth and stomach, then makes the lips and tongue swell. Vomiting is of a brown substance, with bits of dead skin and flesh in it. Skin is cold and clammy and the heart beat feeble and rapid. Death comes from damage to the stomach, asphyxia to the corrosion of the larynx, or congestion of the lungs due to breathing dead material. Also sometimes used to dispose of bodies.

  • Sodium hydroxide Similar to above. Often found in household cleaners

  • Ammonia Colorless and smelly. Not usually used as a murder weapon. If it is consumed in its liquid form, death is usually from corrosion of the larynx. Lungs are congested and frothy, and the blood is dark and resistent to clotting. Exposure to ammonia gas gives a sensation of suffocation, a burning sensation in the mouth and stomach, and vomiting which contains blood and smells of ammonia.

Synthetic Organic Substances

  • Acetylsalicylic Acid (Aspirin) Symptoms: Nausea, though not neccesarily vomiting. Mental confusion and hearing difficulty. Sleepiness leading to coma. Pulse is high, breating is deep and slow. Post-mortem appearance: Dehydration. Fluid on the lungs. Liver and kidneys degernated. Acid and granular urine.

  • Barbituric AcidUsed as sedatives, but addictive and very easy to overdose on. Often used in suicide. Symtoms (of a fatal dose): Headache, vertigo, incontinence. Sleepiness, sometimes with hallucinations, leading to coma. Small pupils won't react to light. Pulse quick and weak. Skin cold and clammy. Breathing loud and heavy, and towards the end may stop periodically and start again. Post-mortem appearance: Congested lungs. Signs of broncho-pneumonia. Frothy fliud in air passages. Brain congested and softened. Full bladder. Urine tests reveals present of barbituate.

  • Chloroform Heavy colorless liquid. Nice smell. Used as anaesthetic, and to render a victim unconsious. However, it's not easy to cholorform a sleeping victim without waking them, and it can take up to 15 minutes to knock the victim out. Victim often convulses as the drug takes effect. Skin blisters on face, where choloroform is in contact with the skin. Prolonged inhalation leads to death by heart failure, and ingestion by heart and liver failure.

    Chloral Hydrate is related. It is usually ingested and, in small doses, can knock someone out very quickly if, for example, placed in their drink. Larger doses cause death by heart and lung failure

  • Cyanide (or Prussic Acid)Quickly fatal in small doses, killing by interfering with the blood's capabilities to absorb oxygen. Faint smell of bitter almonds, though less than the mystery writers tell us.

  • Metaldehyde Found in camping stove fuel and slug pellets. Doesn't taste too nasty, but soon leads to vomiting. Then restlessless, tremors of the arms, mild delirium. Then cramps and convulsions, unconsiousness, coma. Death is from respiratory failure and comes within 3 or 4 days.

  • Nitrobenzine(Oil of Mirbane) Yellow oil in some perfumes and dyes. It reacts with the blood and corrupts it, and also paralyzes the central nervous system. Initial symptoms: burning sensation then numbness in mouth. Pallor. Unconsiousness. Death within about 2 hours by respiratory failure. Post-mortem appearance: Cyanosis - greyness at extremities. Blood dark and thick. Stomach has a red congestion and bleeding under the surface. Organs smell of bitter almonds, like with cyanide.

  • Oxalic Acid Found naturally in rhubarb leaves and also used in some bleaches. Kills by removing calcium from the blood. Symptoms are stomach pains, muscle tremors, rapid breathing, convulsions, coma and death. Can kill with a very small dose. Post-Mortem Appearance Solid calcium oxalate in the kidneys.

  • Paraldehyde Colorless liquid similar in effect to Chloral Hydrate. Tastes horrid and burns, but in small doses produces euphoria and can be addictive. Damages the digestive system, leading to emaciation. Continued use affects the mind and memory. Needs quite a large dose to cause death.

  • Lysol and Phenol Lysol is a disinfectant. Small doses can kill, causing failure of just about everything in the body. Phenol is carbolic acid. Both contain cresol.


  • Aconite Derived from monks hood (a plant). Incredible poisonous, killing with only a tiny dose. Symptoms: Numbness and tingling in mouth and throat starting within minutes or an hour. This soon extends across whole body. Extremities feel cold and clammy. Limbs lose power and sight and hearing dimmed. Mental facilities okay. Pulse weak and variable. Eye dilated Death by respiratory failure between around 10 minutes and three hours, depending on dose.

  • Atropine Found in the belladonna plant. Very poisonous, though not as much so as aconite. Can be absorbed through the skin as well as ingested. Symptoms: Dry mouth and tongue. Difficultly swallowing. Flushed skin leading to rash on upper body. Headache leading to giddiness, hallucination, delirium. Breathing and pulse fast. Dilation of pupils is most distinctive feature - eyes look almost black. Later, signs of paralysis, then coma and death.

  • Cocaine Not often used in murder. An overdose overstimulates the eart fatally.

  • Colchicine Pale yellow crystals from meadow saffron. Kills in small doses. Fatal within 7 to 36 hours. Death is by paralysis of repiratory system.

  • Coniine Oily liquid from hemlock. Not painful to die from it, but progressively paralyses the body until in the end heart or lungs fail. No post-mortem signs except of asphyxia.

  • Gelsemium Seldom used. Symptoms are muscular weakness with slow pulse, dilated pupils. Death from respiratory failure.

  • Nicotine Liquid at room temperature (the only alkaloid, along with coniine, which has this property). Yellowish oil, discolouring to dark brown in light. Poisoning usually done with insecticide, as this is where nicotine is used (only a tiny amount in cigarettes) Absorbed in skin or drunk.Symptoms: Burning sensation in mouth. Vomiting and diarrhoea. Mental confusion and dizziness. Convulsions then death vy paralysis of respiratory system. Death is within minutes - only cyanide is quicker.

  • Opium and Morphine Raw opium very seldom used as a poison as acts slowly and has a strong smell. Morphine is a white crystalline substance extracted from opium. Used as analgesic, but overdose can be fatal. Fatal dose varies but usually about 5 grams. Symptoms start within minutes. Drowsiness. Nausea. Face swollen and colored. Patient feels cold. Cyanosis (greyness of extremities) Eyes dilate to pinpoints that don't react to light and dark (this is the most distinctive symptom). Breathing slow and noisy. Pulse slow and weak. Death is by respiratory failure.

  • Physostigmine Used by some tribes as an "ordeal" poison. Causes excitement and hallucination. Overdose causes vomiting. Severe overdose interferes with heart and causes death.

  • Scopolamine (Hyposcine) Naturally occurring in several plants including belladonna and henbane. Can be administered internally as well as externally. Tiny amounts can be used to treat anxiety or motion sickness. Larger doses break down ability to make reasoned judgments, so has been used as a "Truth Drug" Even larger doses cause hallucinations and floating sensation. Death is when the heart is affected.

    This was found in "Red Museum," in the kidnapped teenagers. Scully described it as an anaesthetic which, in large quantities, is a hallucinogenic and has been used by kidnappers to subdue their victims. She also said it is a controlled substance, only obtainable by doctors.

  • Strychnine Derived from a berry. Colorless solution with a very bitter taste, noticeable even in very weak solutions. Very powerful. 100 miligrams is always fatal, though much smaller doses have killed within 20 minutes. Symptoms: Symptoms come on within 2 or 3 hours - sometimes much faster - but them proceed rapidly. Restlessless. Feeling of suffocation. Face muscles contract and victim looks as if they're grinning. This is followed by very violent and distorting contractions, followed by a period of rest, then an attack of even more violent contractions. Patient is conscious but in agony, unable to speak because of lockjaw. Pulse is incredibly high. Death is during a convulsion, from paralysis of respiratory system. Sometimes confused with tetanus or epilepsy (though different from epilepsy as person is conscious throughout.)


Spanish fly. When crushed and rubbed on skin, causes blisters. Taken orally, a small dose results in kidney damage. Larger doses inflame mouth, throat and stomach. Vomit and urine contain blood. Headache, delirium, convulsions, leading to death.

Inorganic and Metallic Poisons

  • Antimony Usually used in form of a tartar emetic -antimony tartrate - a white metallic powder. Sometimes doesn't work and victim is sick and gets rid of it before it can work. For this reason, and because a large dose is very obviously, is normally used by poisoners in small cumulative doses. Symptoms of large doses Burning in throat. Difficulty swallowing. Stomach pain and vomiting. Faintness. Extreme depression. Pulse is fast at first, then slows down until very slow and irregular. Skin cold and clammy, sweating heavily. Cyanosis (blueness) of extremities. Cramps in legs then elsewhere. Death is by heart failure. Symptoms of cumulative doses Sickness, stomach ache, loss of appetite, diarrhea - just like lots of illnesses.

  • Arsenic Found in lots of places, including occurring naturally in the human body. Used either as yellow oxide, white oxide or vapour, which smells of garlic. White oxide is virtually tasteless and easily masked by food. Can be given cumulatively - fatal dose can build up slowly over time. In this case, symptoms can look like food poisoning. Symptoms vary according to type and method. White oxide poisoning starts with irritation of throat, nausea, faintness, depression. Then vomiting, tinged with blood.and mucus. Severe abdominal pains, exacerbated by touch. Tongue is white and furry and throat constricted. Diarrhea after 12 - 18 hours. Cramps in legs at same time. Pulse weak, rapid and regular. Cyanosis - blueness of extremities caused by lack of oxygen in blood. Death comes when still conscious. Post-Mortem Appearance Found in every part of affected body, even bones and hair, and even years after death. Stomach is very inflamed - even ulcerated. This is even if the poison was administered by being inhaled as a vapor or passing through skin.

  • Barium Used in various soluble compounds. Barium carbonate is used as rat bait. (Insoluble compounds, eg barium sulphate, are harmless and used in barium meal given before X-raying digestive system.) Is an irritant poison, which causes vomiting and thus can get rid of the fatal dose. Symptoms Vomiting. Increased pulse and raised blood pressure. Also attacks central nervous system. Death by heart failure or paralysis. Post-mortem appearance Inflamed throat, stomach, rectum etc.

  • Lead Usually used as one of its salts eg lead acetate. Symptoms are severe stomach pains, vomiting, coms then death. Repeated small doses can cause mental deterioration.

  • MercuryMercury salts are used in a wide variety of legitimate purposes - eg thermometers, paint. Symptoms and fatal doses vary immensely from type to type.

  • Phosphorus Used to be used in matches and rat poison, but no longer. Yellow phosphorus causes liver damage, delirium then coma.

  • Thallium A heavy metal. Salts are colorless, tasteless and easily dissolved in water. Symptoms easily confused with flu. Works very cunningly - it confuses to body so it thinks the thallium is in fact potassium, which is vital for cells and nerves. Symptoms Most distinctive one is hair loss.


Not usually used as murder weapon. Generally only encountered when people eat them by mistake.

Symptoms of most fungus poisons are sickness, diarrhea and stomach pains. When you eat them they often taste bitter and burn, telling you not to eat any further, though some taste delicious (eg Aminita). Then symptoms go away while the poison spreads through body - by the time any really worrying symptoms show up, it's really too late. These later symptoms include giddiness, sweating, fast pulse, anxiety. The more you panic, the faster your heart pumps the poison round the body.

  • Amanita group - Death Cap and Destroying Angel are most deadly - no symptoms for 12 hours, during which poison spreads, then attacks nuclei of cells. Fly agaric is a "magic mushroom" used by lots of tribes for hallucinations.

  • Ergot Parasitic fungus that grows on rye and other cereal. Used to get into bread and cause all sorts of problems, including limbs that suddenly turned black and needed to be amputated. In milder forms, causes tingling at the extremities. While ergot itself does not contain or produce LSD, as is often stated, another fungus (often found in close association) turns a substance which is found in ergot into a hallucinogenic, related to LSD.

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