Ingestion

Overview
Ingestion is the consumption of a substance by an organism. In animals, it is accomplished by taking the substance in through the mouth into the gastrointestinal tract, such as through eating or drinking. In single-celled organisms, ingestion can take place through taking the substance through the cell wall.

Besides nutritional items, other substances which may be ingested include medications, recreational drugs, and substances considered inedible such as foreign bodies or excrement. Ingestion is a common route taken by pathogenic organisms and poisons entering the body.

Ingestion can also refer to a mechanism picking up something and making it enter an internal hollow of that mechanism.

Pathogens
Some pathogens are transmitted via ingestion, including viruses, bacteria, and parasites. Most commonly, this takes place via the fecal-oral route. This commonly takes place via an intermediate step, such as drinking water contaminated by feces or food prepared by workers who fail to practice adequate hand-washing, and is more common in regions where untreated sewage is common. Diseases transmitted via the fecal-oral route include hepatitis A, polio, and cholera.

Some pathogenic organisms are typically ingested by other routes.
 * Larvae of the parasite Trichinella encyst within muscles and are transmitted when the new hosts eat the infected flesh.
 * The parasite Dracunculus is ingested in drinking water, which is contaminated with larvae released as the parasite emerges from the host's body.
 * The bacterium Salmonella most commonly infects humans via consumption of undercooked eggs.

Foreign objects
Disk batteries, or button cells, are often mistakenly ingested, particularly by children and the elderly. They may be mistaken for pills because of their size and shape, or they may be swallowed after being held in the mouth while the battery is being changed. Battery ingestion can cause medical problems including blocked airway, vomiting, irritability, persistent drooling, and rash (due to nickel metal allergy).

Pica is an abnormal appetite for non-nutritive items or for food items in a form not normally eaten, such as flour. Coprophagia is the consumption of feces, a behavior common in some animals.