The first symptoms of food poisoning usually include nausea, vomiting, and diarrhea. Fever may or may not be present. The time it takes for symptoms to appear after eating contaminated food, the severity of the symptoms, and the duration of the illness depend upon the infecting organism and your overall health. These factors may also indicate which harmful organism is responsible for the illness.
Most of the time food poisoning is mild and passes in a few days. However, some types of food poisoning may be more severe:
Salmonella food poisoning may last more than a week and require hospitalization.

Botulism may paralyze nerves, starting at the head and moving down the body. Respiratory failure occurs when the paralysis reaches the lungs, and immediate intensive care is needed to prevent death. Botulism is rare.
E. coli infection can cause serious complications, such as severe blood and kidney problems, in children under 5 years and adults over 65. For more information, see the topic E. coli Infection.
Toxoplasma food poisoning is dangerous to a pregnant woman and her fetus. For more information, see the topic Toxoplasmosis During Pregnancy.
Severity of symptoms is also related to age and general health. The very young and the very old may be hit hardest by food poisoning. Their symptoms may last longer, and even the types of food poisoning that are typically mild can be life-threatening. This is also true for people with impaired immune systems, such as those with chronic illnesses.