Physical contamination is any visible foreign object found in food. Human hair is the most commonly occurring physical contaminate of food. Other common examples of physical contaminates include metal, glass or animal parts not originally part of the food source.
Since it is impossible to tell if a physical food contamination has also caused a chemical contamination or bacterial contamination, food in which foreign objects are found should not be consumed. Chemical contamination is the presence of foreign chemicals in food, bacterial contamination is the presence of harmful bacteria. Although it sometimes happens during preparation, food contamination most often happens during processing. It is sometimes intentional, but the majority of it is accidental. Human hair, for example, is the most common physical contaminate of food. Humans naturally lose several dozen strands of hair each day. Some of these hairs end up in food when hygiene standards in food processing plants are not strictly enforced. Animal parts also typically become physical contaminates in food when proper cleanliness is not maintained. In home kitchens, broken glass and broken knife tips are typically the causes of physical food contamination. On rare occasions, people plant foreign items in food with malicious intent. This is not common, however.