Pica is a medical condition typically defined as the persistent eating of non-food items for a period of at least one month. People with pica crave and eat materials such as dirt, clay, chalk, lead chips, laundry starch, dishwashing soap, chalk, burnt matches, and many other non-food substances. Some of these substances are poisonous.

Many young children have pica at some point during their childhood. Pica can be episodic, meaning that periods of non-food cravings occur only occasionally. While infants and toddlers often eat dirt and other non-food items, this is not considered to be pica because the behavior is not associated with cravings. Some little children just put everything into their mouths as a mode of exploration. Toddlers over the age of two who eat non-food substances on a consistent basis may be considered to have pica.

Pregnant and postpartum women are known to get pica. Pica also occurs among people with certain illnesses such as epilepsy, as well as in persons with mental retardation, autism, or mental illness. Pica is the most common eating disorder among individuals with mental retardation.

Pica occurs throughout the world and is considered an acceptable practice in certain cultures. In Uganda, for example, soils are made available for purchase for the purpose of eating. Eating clay is also a documented practice in parts of the United States.

The specific causes of pica are unknown. Some researchers theorize that pica is caused by a mineral or other dietary deficiency that triggers the cravings. Other research suggest that pica is a response to stress. There is no conclusive evidence to explain the condition.

Eating non-nutritive substances can be harmful to a person's health because it may cause iron deficiency, serious bowel problems, abdominal pain and parasitic infection. Consuming non-food items leaves less opportunity to eat nutritious foods, which may lead to overall malnutrition.

Eating contaminated soils may cause long-term health problems. For example, eating soils contaminated with lead can lead to lead poisoning. Eating soils contaminated with arsenic may cause short-term and long-term arsenic-related illnesses, including cancer.

It is important keep children from eating soils contaminated with chemicals such as lead and arsenic.