A poisonous substance may originate as a mineral, vegetable, or an animal and it may assume the form of a solid, liquid, or gas. Poisons in humans are usually classified according to their effects as corrosives, irritants, or systemic poisons. Corrosives ones include strong acids or alkalis that cause local tissue destruction, externally or internally; that is, they burn the skin or the lining of the stomach. Vomiting occurs immediately, and the vomitus is intermixed with blood. Common or so-called household corrosive poisons include hydrochloric acid, carbolic acid, bichloride of mercury, and ammonia. Irritants such as arsenic, mercury, iodine, and laxatives act directly on the mucous membrane, causing gastrointestinal irritation or inflammation accompanied by pain and vomiting; diluted corrosive poisons also have these effects. Irritants include cumulative poisons, those substances that can be absorbed gradually without apparent harm until they suddenly take effect.

Systemic poisons act upon the central nervous system or upon important body organs until they affect the respiratory and circulatory systems. These poisons can cause convulsions, or delirium. Systemic poisons include narcotics, potassium cyanide, and some organic solvents. Also included in this category is one of the most dangerous poisons known, botulin toxin a potent bacterial toxin that is the cause of acute food poisoning.

Blood poisoning, also bacterial in nature, is a condition that occurs when virulent micro-organisms invade the bloodstream through a wound or an infection. Symptoms include chills, fever, prostration, and often infections or secondary abscesses in various organs. Most poison gases also affect the bloodstream. Because these gases restrict the body's ability to absorb oxygen, they are often considered in a separate category called asphyxiants, to which group ordinary carbon monoxide belongs. Gas poisons, however, may also be corrosives or irritants.

About 50 per cent of all human poisoning in the West involve commonly used drugs or household products such as aspirin, insecticides, and cosmetics. Because barbiturates are easily available, toxic effects resulting from their misuse are not infrequent. Acute poisoning may result from over dosage or interaction with other drugs, especially alcohol. The victim of acute barbiturate poisoning may become agitated and nauseated, or may pass into a deep sleep marked by increasingly shallow respiration. Coma and heart failure may follow. Chronic barbiturate poisoning, caused by prolonged use of the drugs, is usually marked by gastrointestinal irritation, loss of appetite, and anemia. In advanced stages of chronic barbiturate poisoning the victim may show mental confusion.

Various treatments may counteract the effect of a poison. In most cases the use of dilution is advisable, that is, the ingestion of large quantities of water or milk. In other cases it is advisable to use an emetic, a substance that induces vomiting and rids the stomach of certain poisons. An emetic may act locally, as on the gastric nerves, or systematically on the part of the brain that causes the vomiting. Household emetics, which act locally, include a tablespoon of salt dissolved in warm water or two tablespoons of mustard dissolved in a pint of water. Emetics must not be given to a person who has swallowed a corrosive poison. An antidote, unlike an emetic, is a remedy that counteracts the effects of a poison chemically, although it may result indirectly in vomiting. An antidote may work against a poison by neutralizing it, rendering it insoluble, absorbing it, isolating it, or producing an opposite physiological effect generally. In any instance of poisoning, it is imperative that remedial treatment be started immediately.

Dr.Badruddin Khan - About the Author: Dr. Badruddin Khan teaches Chemistry in the University of Kashmir, Srinagar, India.