What causes food poisoning?

Food poisoning is illness caused by eating contaminated food. Infectious organisms form the most common cause of food poisoning. These organisms or their toxins can contaminate food at any point of production processing, transportation, cooking, serving or eating. The common pathogens causing food poisoning are bacteria like salmonella, shigella, viruses like Norswalk like virus, hepatitis A, protozoa like amoebiasis, Giardiasis, parasites including tape worm, round worm. Bacteria like Clostridium cause severe food poisoning due to release of toxin. Few cases can occur due to chemicals like pesticides, heavy metals like lead, cadmium or food allergies.