Activated charcoal is estimated to reduce up to 60% of poisonous substances being absorbed.
Activated charcoal is made from organic materials such as wood pulp and then treated to further enhance its absorptive powers. Once ingested, it binds with certain chemicals in the digestive tract, preventing them from being absorbed into your system and causing harm.
Activated charcoal is used in the emergency treatment of certain kinds of poisoning. It helps prevent the poison from being absorbed from the stomach into the body. Sometimes, several doses of activated charcoal are needed to treat severe poisoning. Ordinarily, this medicine is not effective and should not be used in poisoning if corrosive agents such as alkalis (lye) and strong acids, iron, boric acid, lithium, petroleum products (e.g., cleaning fluid, coal oil, fuel oil, gasoline, kerosene, paint thinner), or alcohols have been swallowed, since it will not prevent these poisons from being absorbed into the body.
Activated charcoal is often given after gastric lavage-the technique often called the stomach pump. Gastric lavage is only effective immediately after swallowing a toxic substance (within about one-half hour) and does not reach beyond the stomach as activated charcoal does.
Activated charcoal's most important use is for treatment of poisoning. It helps prevent the absorption of most poisons or drugs by the stomach and intestines. In addition to being used for most swallowed poisons in humans, charcoal has been effectively used in dogs, rabbits, rats, and other animals, as well. It can also adsorb gas in the bowels and has been used for the treatment of gas or diarrhea. Charcoal's other uses such as treatment of viruses, bacteria, bacterial toxic byproducts, snake venoms and other substances by adsorption have not been supported by clinical studies.
Activated charcoal is good at trapping carbon-based impurities ("organic" chemicals), as well as things like chlorine. Many other chemicals are not attracted to carbon at all -- sodium, nitrates, etc. -- so they pass right through. This means that an activated charcoal filter will remove certain impurities while ignoring others.