Pica is a medical disorder characterized by an appetite for non-nutritive substances. The condition's name comes from the Latin word for magpie, a bird which is reputed to eat almost anything. Pica is seen in all ages, particularly in pregnant women, small children, and those with developmental disabilities. Pica can also be found in animals, most commonly in dogs.

Pica in children, while common, can be dangerous. Children eating paint containing lead may suffer brain damage from lead poisoning. There is a similar risk from eating earth near roads that existed prior to the phaseout of tetra-ethyl lead in petrol or prior to the cessation of the use of contaminated oil (either used, or containing toxic PCBs or dioxin) to settle dust.

Research on the causes of pica suggests that the disorder is caused by mineral deficiency in many cases, typically iron deficiency. More recently, cases of pica have been tied to the obsessive–compulsive spectrum. Sensory, physiological, cultural, and psychosocial perspectives have also been used to explain the causation of pica. For example, people in various cultures believe that eating dirt will help them incorporate magical spirits into their bodies.

In the Glore Psychiatric Museum, St. Joseph, Missouri, USA, there is an arrangement of 1,446 items swallowed by a patient and removed from her intestines and stomach. She died during surgery from bleeding caused by 453 nails, 42 screws, safety pins, spoon tops, and salt and pepper shaker tops.

In One Hundred Years of Solitude, by Gabriel Garcia Marquez, the character Rebeca has an addiction to eating earth and other non-food substances.

Some types of Pica

Amylophagia (consumption of starch)
Coprophagia (consumption of feces)
Geophagy (consumption of soil, clay, or chalk)
Hyalophagia (consumption of glass)
Mucophagia (consumption of mucus)
Odowa (soft stones eaten by pregnant women in Kenya)
Pagophagia (pathological consumption of ice)
Self-cannibalism (rare condition where body parts may be consumed; see also Lesch-Nyhan syndrome)
Trichophagia (consumption of hair or wool)
Urophagia (consumption of urine)
Xylophagia (consumption of wood)