Most food poisonings manifest within the first 2 to 6 hours after consumption of contaminated food or water. This is called the incubation period and may be longer or shorter depending upon the cause of infection.

General symptoms of food poisoning

The common general symptoms include (1-5) –

• Abdominal cramps and pain
• Nausea and vomiting
• Headache
• Weakness that may be severe or even lead to paralysis
• Diarrhea – May be watery and copious or may be bloody at times.
• Fever with chills and tremors or rigors
• Muscle pains and aches

Characteristic symptoms of specific infections

Specific infections may have certain characteristic symptoms. Some of these maybe (2, 5) –

• Infection with Escherichia coli (E. coli) – May lead to diarrhea with very little stool and large amounts of blood also called hemorrhagic colitis. This may occur up to 3 days after eating the tainted food.
• Norovirus and viral infections – Mild infection with typical symptoms may be seen. Hepatitis A infection may lead to liver damage and jaundice in addition. Rotavirus infection often affects infants and may lead to severe watery diarrhea.
• Clostridium botulinum – Typically may lead to weakness, blurred vision, double vision, paralysis, respiratory failure and even death.
• Shigella, Salmonella and Campylobacter - May lead to fever, bloody diarrhoea, chills etc.
• Mushroom poisoning – May lead to rapid onset liver damage, affection of the brain with delirium (confusion), vision problems, kidney failure and death.
• Fish poisoning may lead to typical symptoms of food poisoning along with allergic symptoms like itching, swelling of the face, difficulty in swallowing and breathing that may lead to death. This is called anaphylaxis.

Symptoms which signal the help of a physician is needed

Most cases of food poisoning resolve by themselves at home. However, help from the physician needs to be sought if (3, 5) –

• There is severe vomiting and diarrhea for more than 48 or 72 hours respectively
• Inability to keep anything down
• Blood in vomit or stools
• Seizures
• Confusion or delirium
• Blurring or difficulty in vision
• Slurring speech
• Paralysis or severe weakness
• Signs of severe dehydration like dry mouth, sunken eyes and inability to pass urine for long durations.
• If the patient is an elderly person, pregnant woman or child below three years.
• Symptoms after recent foreign travel
• Patient has other conditions like HIV/AIDS, cancer and undergoing chemotherapy, kidney disease etc.
• If the eyes turn yellow (symptom of jaundice)
• One or more joints swell or a rash breaks out on the ill person's skin.

Sources:

1. http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002618/
2. http://www.umm.edu/altmed/articles/food-poisoning-000064.htm
3. http://www.nhs.uk/Conditions/Food-poisoning/Pages/Symptoms.aspx
4. www.webmd.com/.../food-poisoning-and-safe-food-handling-symptoms
5. www.emedicinehealth.com/.../page3_em.htm#Food Poisoning Symptoms