A poison is a substance that, in small amounts, disrupts the structure and/or function of cells.

Poisoning occurs when a poison is taken into the body. Poisons may be swallowed, inhaled, absorbed through the skin, or injected under the skin (as with an insect sting). They may also originate within the body, for example when bacteria produce endotoxins, or when metabolic disorders produce poisonous substances or allow them to accumulate.

Poisoning may be acute, if a large amount of poison enters the body in a short time, or chronic, resulting from a gradual accumulation of poison that is not quickly eliminated from the body. Unintentional poisoning occurs most commonly in young children.

Adults may be poisoned by mistaking the dosage of a prescribed drug, by taking very high doses of vitamin or mineral supplements, by exposure to poisonous substances in industry, or by drug abuse. Poisoning may also be a deliberate attempt to commit suicide. Antidotes may be available to counteract the effects of the poison. 

Poisoning by drugs and chemicals - technical

Poisoning by drugs and chemicals - general management - technical

Poisoning by drugs and chemicals - methods to increase poison elimination - technical

Poisoning by specific drugs (including substances of abuse) - clinical features and treatment - Amfetamines to Diuretics - technical

Poisoning by specific drugs - clinical features and management - Ethanol to Opiates - technical

Poisoning by specific drugs clinical features and management - Paracetamol (Acetominophen) to Warfarin - technical

Poisoning in more detail


Poisoning occurs when any substance interferes with normal body functions after it is swallowed, inhaled, injected, or absorbed. The branch of medicine that deals with the detection and treatment of poisons is known as toxicology.


Poisonings are a common occurrence and can be intentional or unintentional. About 10 million cases of poisoning occur in the United States each year. In 80% of the cases, the victim is a child under the age of five. About 50 children die each year from poisonings. Curiosity, inability to read warning labels, a desire to imitate adults, and inadequate supervision lead to childhood poisonings.

The elderly are the second most likely group to be poisoned. Mental confusion, poor eyesight, and the use of multiple drugs are the leading reasons that this group has a high rate of accidental poisoning. A substantial number of poisonings also occur as suicide attempts or drug overdoses.

According to the Centers for Disease Control (CDC), In 2008, unintentional poisoning caused about 732,316 emergency department (ED) visits, and 23% of those unintentional poisonings (166,015) resulted in hospitalization or transfer to another facility.


Poisons are common in the home and workplace, yet there are basically two major types. One group consists of products that were never meant to be ingested or inhaled, such as shampoo, paint thinner, pesticides, houseplant leaves, and carbon monoxide. The other group contains products that can be ingested in small quantities, but which are harmful if taken in large amounts, such as pharmaceuticals, medicinal herbs, or alcohol. Other types of poisons include the bacterial toxins that cause food poisoning, such as Escherichia coli; heavy metals, such as the lead found in the paint on older houses; and the venom found in the bites and stings of some animals and insects. The staff at a poison control center and emergency room doctors have the most experience diagnosing and treating poisoning cases.

Causes and symptoms

The effects of poisons are as varied as the poisons themselves. However, the exact mechanisms of only a few are understood. Some poisons interfere with metabolism. Others destroy the liver or kidneys. Some examples include heavy metals and some pain relief medications, including acetaminophen (Tylenol) and nonsteroidal anti–inflammatory drugs (Advil, Ibuprofen). A poison may severely depress the central nervous system, leading to coma and eventual respiratory and circulatory failure. Potential poisons in this category include anesthetics (e.g. ether and chloroform), opiates (e.g., morphine and codeine), and barbiturates. Some poisons directly affect the respiratory and circulatory systems.

Carbon monoxide causes death by binding with hemoglobin that normally transports oxygen throughout the body. Certain corrosive vapors trigger the body to flood the lungs with fluids, effectively drowning the person. Cyanide interferes with respiration at the cellular level. Another group of poisons interferes with the electrochemical impulses that travel between neurons in the nervous system. Yet another group, including cocaine, ergot, strychnine, and some snake venoms, causes potentially fatal seizures.

Severity of symptoms can range from headache and nausea to convulsions and death. The type of poison; the amount and time of exposure; and the age, size, and health of the victim are all factors that determine the severity of symptoms and the chances for recovery.

Plant poisoning

There are more than 700 species of poisonous plants in the United States. Plants are second only to medicines in causing serious poisoning in children under age five. There is no way to tell by looking at a plant if it is poisonous. Some plants, such as the yew shrub, are almost entirely toxic: needles, bark, seeds, and berries. In other plants, only certain parts are poisonous.

The bulb of the hyacinth and daffodil are toxic, but the flowers are not, while the flowers of the jasmine plant are the poisonous part. Moreover, some plants are confusing because portions of them are eaten as food while other parts are poisonous. For example, the fleshy stem (tuber) of the potato plant is nutritious. However, its roots, sprouts, and vines are poisonous.

The leaves of tomatoes are poisonous, while the fruit is not. Rhubarb stalks are good to eat, but the leaves are poisonous. Apricots, cherries, peaches, and apples all produce healthful fruit, but their seeds contain a form of cyanide that can kill a child if chewed in sufficient quantities. One hundred milligrams of moist, crushed apricot seeds can produce 217 mg of cyanide

Common houseplants that contain some poisonous parts include:

  • Aloe
  • Amaryllis
  • Cyclamen
  • Dumb cane (also called Dieffenbachia)
  • Philodendron

Common outdoor plants that contain some poisonous part include:

  • Bird of paradise flower
  • Buttercup
  • Castor bean
  • Chinaberry tree
  • Daffodil
  • English ivy
  • Eucalyptus
  • Foxglove
  • Holly
  • Horse chestnut
  • Iris
  • Jack–in–the–pulpit
  • Jimsonweed (also called thornapple)
  • Larkspur
  • Lily–of–the–valley
  • Morning glory
  • Nightshade (several varieties)
  • Oleander
  • Potato
  • Rhododendron
  • Rhubarb
  • Sweet pea
  • Tomato
  • Wisteria
  • Yew

Symptoms of plant poisoning range from irritation of the skin or mucous membranes of the mouth and throat to nausea, vomiting, convulsions, irregular heartbeat, and even death. It is often difficult to tell if a person has eaten a poisonous plant because there are no tell–tale empty containers and no unusual lesions or odors around the mouth.

Many cases of plant poisoning involve plants that contain hallucinogens, such as peyote cactus buttons, certain types of mushrooms, and marijuana. A recent case of plant poisoning in France concerned Datura, or moonflower, a plant that has become popular with young people trying to imitate Native American puberty rites.

Other cases of plant poisoning result from the use of herbal dietary supplements that have been contaminated by toxic substances. The Food and Drug Administration (FDA) has the authority to monitor herbal products on the market and issue warnings about accidental poisoning or other adverse affects associated with these products. For example, in 2002 a manufacturer of nettle capsules found to contain lead recalled the product following a warning from the FDA. Other dietary supplements have been found to contain small quantities of prescription medications or even toxic plants.

Household chemicals

Many products used daily in the home are poisonous if swallowed. These products often contain strong acids or strong bases (alkalis). Toxic household cleaning products include:

  • ammonia
  • bleach
  • dishwashing liquids
  • drain openers
  • floor waxes and furniture polishes
  • laundry detergents, spot cleaners, and fabric softeners  
  • mildew removers
  • oven cleaners
  • toilet bowl cleaners

Personal care products found in the home can also be poisonous. These include:

  • deodorant
  • hairspray
  • hair straighteners
  • nail polish and polish remover
  • perfume
  • shampoo

Signs that a person has swallowed one of these substances include evidence of an empty container nearby, nausea or vomiting, and burns on the lips and skin around the mouth if the substance was a strong acid or alkali. The chemicals in some of these products may leave a distinctive odor on the breath.


Both over–the–counter and prescription medicines can help the body heal if taken as directed.

However, when taken in large quantities, or with other drugs where there may be an adverse interaction, they can act as poisons. Drug overdoses, both accidental and intentional, are the leading cause of poisoning in adults. Medicinal herbs should be treated like pharmaceuticals and taken only in designated quantities under the supervision of a knowledgeable person. Herbs that have healing qualities when taken in small doses can be toxic in larger doses, or may interact with prescription medications in unpredictable ways.

Drug overdoses cause a range of symptoms, including excitability, sleepiness, confusion, unconsciousness, rapid heartbeat, convulsions, nausea, and changes in blood pressure. The best initial evidence of a drug overdose is the presence of an empty container near the victim.

Other causes of poisonings

People can be poisoned by fumes they inhale. Carbon monoxide is the most common form of inhaled poison. Other toxic substances that can be inhaled include:

  • farm and garden insecticides and herbicides
  • gasoline fumes
  • insect repellent
  • paint thinner fumes


Initially, poisoning is suspected if the victim shows changes in behavior and signs or symptoms previously described. Hallucinations or other psychiatric symptoms may indicate poisoning by a hallucinogenic plant. Evidence of an empty container or information from the victim are helpful in determining exactly what substance has caused the poisoning. Some acids and alkalis leave burns on the mouth. Petroleum products, such as lighter fluid or kerosene, leave a distinctive odor on the breath. The vomit may be tested to determine the exact composition of the poison. Once hospitalized, the patient may be given blood and urine tests to determine his or her metabolic condition.


Treatment for poisoning depends on the poison swallowed or inhaled. Contacting the poison control center or hospital emergency room is the first step in getting proper treatment. The poison control center’s telephone number is often listed with emergency numbers on the inside cover of the telephone book, or it can be reached by dialing the operator. The poison control center will ask for specific information about the victim and the poison, then give appropriate first aid instructions. If the patient is to be taken to a hospital, a sample of vomit and the poison container should be taken along, if they are available.

Most cases of plant poisoning are treated by inducing vomiting, if the patient is fully conscious. Vomiting can be induced by taking syrup of ipecac, an over–the–counter emetic available at any pharmacy.

For acid, alkali, or petroleum product poisonings, the patient should not vomit. Acids and alkalis can burn the esophagus if they are vomited, and petroleum products can be inhaled into the lungs during vomiting, resulting in pneumonia.

Once under medical care, doctors have the option of treating the patient with a specific remedy to counteract the poison (antidote) or with activated charcoal to absorb the substance inside the patient’s digestive system. In some instances, pumping the stomach may be required. This technique, which is known as gastric lavage, involves introducing 20–30 mL of tap water or nine percent saline solution into the patient’s digestive tract and removing the stomach contents with a siphon or syringe. The process is repeated until the washings are free of poison. Medical personnel will also provide supportive care as needed, such as intravenous fluids or mechanical ventilation.

If the doctor suspects that the poisoning was not accidental, he or she is required to notify law enforcement authorities. Most cases of malicious poisoning concern family members or acquaintances of the victim, but the number of intentional random poisonings of the general public has increased in recent years. A case reported in 2003 involved the use of nicotine to poison 1700 pounds of ground beef in a Michigan supermarket. Over a hundred persons fell ill after eating the poisoned beef.


The outcome of poisoning varies from complete recovery to death, and depends on the type and amount of the poison, the health of the victim, and the speed with which medical care is obtained.


Most accidental poisonings are preventable. The number of deaths of children from poisoning has declined from about 450 per year in the 1960s to less than 50 each year since the 1990s. This decline has occurred mainly because of better packaging of toxic materials and better public education.

Actions to prevent poisonings include:

  • removing plants that are poisonous
  • keeping medicines and household chemicals locked and in a place inaccessible to children
  • keeping medications in child–resistant containers
  • never referring to medicine as ‘‘candy’’
  • keeping cleaners and other poisons in their original containers
  • disposing of outdated prescription medicines
  • not purchasing over–the–counter medications with damaged protective seals or packaging
  • avoiding the use of herbal preparations not made by a reputable manufacturer