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Table of Contents > Conditions > Food Poisoning
Food Poisoning
Signs and Symptoms
What Causes It?
Who's Most At Risk?
What to Expect at Your Provider's Office
Treatment Options
Treatment Plan
Drug Therapies
Complementary and Alternative Therapies
Prognosis/Possible Complications
Following Up
Supporting Research

Food poisoning is the result of eating microbes or toxins in contaminated food. Cases can affect one person or can occur as an outbreak in a group of people who all ate the same contaminated food. While many cases are the result of bacteria, some cases can be the result of poisonous components of plants and animals. Food poisoning affects between 60 and 80 million people worldwide each year, resulting in approximately 6 to 8 million deaths.

Signs and Symptoms

Food poisoning from bacteria causes nausea, vomiting, abdominal cramping, and diarrhea. Specific bacteria may cause these signs and symptoms:

  • Clostridium botulinum (C. botulinum, or botulism): weakness, blurred vision, sensitivity to light, double vision, paralyzed eye nerves, difficulty speaking, trouble swallowing, paralysis that spreads downward, respiratory failure, death 
  • C. botulinum in infants: impaired physical growth (failure to thrive), constipation, paralysis, sudden infant death 
  • Vibrio cholerae (V. cholerae, or cholera): stools that are liquid with a whitish tinge
  • Salmonella spp., Shigella spp., and Campylobacter jejuni (C. jejuni): fever, chills, bloody diarrhea 
  • Escherichia coli (E. coli): hemorrhagic colitis (bleeding from inflamed large intestine) 
  • Yersinia spp.: symptoms similar to appendicitis; delayed immune reaction including arthritis and/or red, tender bumps under the skin (erythema nodosum); sometimes bloody stool 

Mushroom poisoning causes red blood cell problems, stomach flu, delirium (confusion), vision difficulties, heart muscle problems, kidney failure, and death of liver tissue. It causes death in about half of the people affected unless treated right away.

Fish poisoning causes nausea, vomiting, diarrhea, abdominal pain, dizziness, and headache. Specific types of fish can cause other signs and symptoms, such as:

  • Scombroid poisoning: flushing (redness of the face and neck)
  • Ciguatera toxicity: numbness or tingling around the mouth, feeling of loose teeth, impaired touch sensation of hot as cold and cold as hot, itching, muscle and joint pain, slow heart rate, low blood pressure; alcohol may cause symptoms to recur or become worse 
  • Puffer fish poisoning: numbness or tingling around the mouth, trouble coordinating movement, difficulty swallowing, excess saliva, twitching, loss of ability to talk, convulsions, paralysis that spreads upward, respiratory failure, death 
  • Shellfish poisoning: numbness or tingling around the mouth or in the arms and legs; trouble swallowing; difficulty speaking; death from anaphylactic shock, a severe allergic reaction 

What Causes It?

Usually bacteria, protozoans (such as amoebas), and algae cause food poisoning. But sometimes poisonous parts of plants and animals are the cause.

Common bacterial toxins include:

  • E. coli in undercooked hamburger, unpasteurized apple juice or cider, raw milk, contaminated water (or ice); can be spread from person to person 
  • Traveler's diarrhea (another form of E. coli) from fruits, leafy vegetables, unsanitary drinking water and ice made from this water, and imported cheese 
  • Listeria monocytogenes (L. monocytogenes) in cole slaw, dairy products (mostly soft cheeses from outside the United States), and cold, processed meats 
  • Salmonella spp. in poultry, beef, eggs, or dairy products 
  • Shigella spp. from raw vegetables or from cool, moist foods (such as potato and egg salads) that are handled after cooking
  • Staphylococcus aureus (S. aureus) in protein-rich foods, especially ham, eggs, custard-filled pastries, mayonnaise, and potato salad, often from the hands of food handlers 
  • Bacillus cereus in uncooked grains, especially rice 
  • C. jejuni in raw milk and poultry 
  • C. botulinum in undercooked home-canned foods; in children under 1 year of age, mostly from honey but also from corn syrup 
  • Clostridium perfringens (C. perfringens) in meat and poultry dishes and gravies, mostly foods that were cooked more than 24 hours before eating and were not reheated well enough 
  • V. cholerae in bivalve (two-shelled) shellfish (such as mussels, clams, oysters, and scallops), raw shellfish, and crustaceans (such as lobsters, shrimp, and crabs) 
  • Yersinia in contaminated meats; less common in United States than other food poisonings; more common in Scandinavia 

Common types of fish poisoning include the following:

  • Scombroid poisoning from bacteria in dark meat fish (tuna, bonito, skipjack, mahi-mahi, mackerel) that are not refrigerated well 
  • Ciguatera poisoning in tropical fish (grouper, surgeonfish, snapper, barracuda, moray eel) that have eaten the plankton Gambierdiscus toxicus 
  • Puffer fish poisoning from the organs and flesh of puffer fish 
  • Poisoning from bivalve shellfish that feed on red tide (plankton)

Mushroom poisoning occurs from eating wild poisonous mushrooms, especially Amanita phalloides.

Who's Most At Risk?

Infants and the elderly are at greater risk for food poisoning. A person is also at greater risk if any of the following is true:

  • Pre-existing medical condition, such as chronic kidney failure or diabetes 
  • Antibiotic or histamine-blocking medicines 
  • Sickle-cell anemia and other problems with red blood cells 
  • Weakened immune system
  • Travel in an area where contamination is more likely 
  • Food shortage 

Listeriosis is most common in pregnant women, fetuses, and people with immune problems. When a fetus is infected with L. monocytogenes, the fetus may be born prematurely or die.

What to Expect at Your Provider's Office

Your healthcare provider will examine you for signs and symptoms of food poisoning, such as stomach problems, and of dehydration. Your provider may also ask about foods you have eaten recently. Tests of your vomit, blood, and stool, and tests of any leftover food can identify the cause.

Your healthcare provider may also use these tests:

  • Sigmoidoscopy (putting a thin, tube-like tool into the anus) to look for bleeding or sores
  • Electromyography (a test to measure electric impulses in the muscles) to check for botulism
  • Lumbar puncture (a test of fluid from the spine) for signs and symptoms related to central nervous system disorders 

Treatment Options

These steps can help prevent food poisoning:

  • Be very careful to wash your hands and to clean any dishes or utensils when you are making or serving food.
  • Promptly refrigerate any food you will not be eating right away.
  • If you take care of young children, wash your hands often and dispose of diapers carefully so that bacteria can't spread to other surfaces or people.
  • If you make canned food at home, make sure to follow proper canning techniques to prevent botulism.
  • Don't feed honey to children under 1 year of age.
  • Don't eat wild mushrooms.
  • When traveling where contamination is more likely, eat only hot, freshly cooked food. Drink water only if it's been boiled. Don't eat raw vegetables or unpeeled fruit.
  • Always refrigerate fish well.
  • Don't eat tropical fish caught during blooms of poison plankton.
  • Eat puffer fish only in specially licensed restaurants with chefs trained to cook it.
  • Don't eat shellfish exposed to red tides.

If others may also have eaten a food that made you sick, let them know. If you think the food was contaminated when you bought it from a store or restaurant, tell the staff and your local health department.

Treatment Plan

Treatment is meant to help support recovery and relieve symptoms. For instance, treatment may help replace fluids and electrolytes (such as sodium, potassium, magnesium, and chloride), help the person breathe, or stop vomiting or diarrhea. In most cases, healthcare providers do not prescribe antibiotics because they may prolong diarrhea. If the person has eaten certain toxins (such as from mushrooms or shellfish), the provider may take steps to empty and clean out his or her stomach (a process called lavage) and administer activated charcoal, which can absorb the remaining toxin.

Drug Therapies

Depending on the symptoms and the cause of food poisoning, a healthcare provider may prescribe drugs including these:

  • Antibiotics, such as ampicillin; similarly, TMP-SMX, doxycycline, or ciprofloxacin, are given to prevent or treat traveler's diarrhea 
  • Antitoxin to neutralize toxins from C. botulinum 
  • Amitriptyline to control the numbness and tingling from ciguatera poisoning 
  • Apomorphine or ipecac syrup to cause vomiting and help rid the body of toxin 
  • Atropine for mushroom poisoning 
  • Diphenhydramine and cimetidine for fish poisoning
  • Mannitol for nerve-related symptoms of ciguatera poisoning

Complementary and Alternative Therapies

Animal studies have shown that certain vitamins and nutrients, such as vitamin A and calcium, may be particularly effectively in protecting against some food toxins while others, such as fish oil, may actually worsen the effects of toxins. Milk thistle is an herb commonly used in Europe as a primary treatment for mushroom poison. Homeopathy is particularly promising for the treatment of diarrhea in children (which is sometimes caused by food poisoning) in developing countries.


The following general nutritional guidelines may be helpful in the case of food poisoning:

  • Drink plenty of fluids (to prevent dehydration)
  • Drink barley or rice water (to soothe inflamed stomach or intestine)
  • Lactobacillus acidophilus (for those taking antibiotics)

Advice more specific to food poisoning includes:

  • Alpha-Lipoic Acid -- Several reports indicate that alpha-lipoic acid, an antioxidant commonly found in broccoli, spinach, and beef, may be helpful in the treatment of Amanita poisoning. The usual dose for the supplement form is 50 mg twice a day or 100 mg once a day.
  • Coumarins -- Lab studies have shown that coumarins, substances found in many fruits and vegetables, may help stop the growth of E. coli. It is not clear however, whether these test tube studies will translate into coumarins offering a protective effect against E. coli infection in humans. To prevent traveler's diarrhea, fruits and vegetables should be peeled, washed carefully, and preferably cooked before ingestion (see section entitled Prevention).

Many animal studies have investigated the use of vitamins, minerals, and supplements to treat food poisoning. The most promising include:

  • Vitamin A -- Rats infected with Salmonella appeared to eliminate the bacteria from their bodies faster when pretreated with vitamin A than with placebo, according to one study. They also gain more weight and have a greater immune response than placebo-treated rats. Another study suggests that vitamin A-deficient rats may actually be more prone to Salmonella infection.
  • Calcium phosphate -- One animal study suggests that rats receiving calcium phosphate supplements may be protected from infection by Salmonella enteritidis poisoning. Researchers theorize that calcium phosphate helps to defend against certain organisms found in some foods that can cause disease.
  • Fish Oil -- In a study of mice infected with the bacteria, Listeria, animals that regularly consumed diets rich in fish oil had significantly more bacteria in their spleens than animals that consumed diets rich in lard or soybean oil. Until researchers can determine what these results mean to humans, people who have Listeria infection should avoid foods containing fish oil.


Use of the following for people with a specific food poisoning is well documented:

  • Milk Thistle (Silybum marianum) is one of the most effective herbs for liver disorders and is widely used in Europe to treat Amanita mushroom poisoning. Studies have shown that patients with Amanita poisoning can be effectively treated with silibinin (the primary active component of milk thistle) up to 48 hours after eating the deadly mushrooms.

Animal studies of Chinese and Japanese combination herbal remedies used for L. monocytogenes support the traditional use for this type of food poisoning. A few of the active ingredients include:

  • Asian ginseng (Panax ginseng)
  • Astragalus root (Astragalus membranaceus)
  • Chinese cinnamon bark (Cinnamomum aromaticum)
  • Ginger root (Zingiber officinale)
  • Licorice (Glcyrrhizae glabra)
  • Peony root (Paeonia officinalis)
  • Skullcap (Scutellaria lateriflora)

When considering use of combination remedies, it is best to seek the advice of an appropriately trained, licensed, and certified herbalist or traditional Chinese doctor who will guide your individual treatment; the substances tend to complement one another and work in tandem, not separately.

Laboratory studies (those performed in test tubes) suggest that the following substances have activity against particular organisms that may cause food poisoning:

  • Bittervine (Mikania micranthu) - A plant extract from a traditional Jamaican folk medicine shows activity against several types of bacteria, including S. aureus and E. coli.
  • Tea Tree Oil (Melaleuca alternifolia) -- Lab studies have shown that the essential oil of the tea tree has activity against E. coli.
  • Thyme -- The essential oil of thyme (Thymus vulgaris) has killed the bacteria Salmonella typhimurium; additional lab studies also suggest that thymol (a part of thyme oil) has activity against S. aureus.

While these lab results are interesting, they do not necessarily translate into treatment for people, particularly the tea tree oil and thyme trials because essential oils should generally not be ingested. Thyme is available in a dried herb and is used to help digestion and to treat symptoms of gastritis (inflammation of the stomach lining); however, it is not known whether the dried herb would have the same activity as the oil against the bacteria mentioned.

  • Barberry (Berberis vulgaris) has also been used traditionally to treat diarrhea from infectious causes such as E. coli and V. cholera and, therefore, may help ease this symptom in some people with food poisoning.


In a recent study of children with acute diarrhea, those who received an individualized homeopathic treatment for five days had a significantly shorter duration of diarrhea than children who received placebo. Before prescribing a remedy, homeopaths take into account a person's constitutional type. In homeopathic terms, a person's constitution is his or her physical, emotional, and intellectual makeup. An experienced homeopath assesses all of these factors when determining the most appropriate remedy for a particular individual.

  • Arsenicum album — for foul-smelling diarrhea from food poisoning or traveler's diarrhea with burning sensation in the abdomen and around the anus; this remedy is most appropriate for individuals who feel exhausted yet restless and whose symptoms tend to worsen in the cold and improve with warmth; vomiting may also occur; Arsenicum may also be used to prevent diarrhea when traveling 
  • Chamomilla — for greenish, frothy stool that smells like rotten eggs; used primarily for children, especially those who are irritable, argumentative, and difficult to console 
  • Calcarea carbonica — for children who fear being in the dark or alone and who perspire heavily while sleeping; stools have a sour odor
  • Podophyllum —for explosive, gushing, painless diarrhea that becomes worse after eating or drinking; exhaustion often follows bowel movements and the individual for whom this remedy is appropriate may experience painful cramps in lower extremities 
  • Sulphur — for irritable and weepy children; may have a red ring around the anus and diarrhea with the odor of rotten eggs 

Prognosis/Possible Complications

Most food poisoning clears up on its own with no aftereffects. However, with mushroom poisoning, as many as 50% of people die; with botulism, less than 10% die. Some people may need help breathing for months afterwards. More than half of poisonings from puffer fish are fatal. Death is rare in other fish poisonings, but nerve-related symptoms can continue for months.

The following are some possible aftereffects of food poisoning:

  • After shigellosis, white blood cell problems and kidney problems
  • After E. coli infection, kidney problems and bleeding problems
  • After yersiniosis, arthritis or tender bumps under the skin
  • After botulism, long hospital stays (1 to 10 months) with fatigue and difficulty breathing for 1 to 2 years or respiratory failure
  • After C. perfringens infection, serious inflammation, bleeding, and tissue death in the intestines
  • After salmonellosis, Reiter's syndrome (an arthritis-like disease) and inflammation of the heart lining
  • After campylobacteriosis, Guillain-Barré syndrome (a nerve disease)

Following Up

For severe cases of food poisoning, the person may need to stay in the hospital to receive fluids and electrolytes, and so healthcare providers can monitor breathing. Providers may need to intubate the person (insert a tube down his or her throat) or connect him or her to a machine to help with breathing. Dialysis may be required. Cathartics (substances that help the body remove waste), enemas, and lavage may help eliminate toxins.

Supporting Research

Beers MH, et al. The Merck Manual: Diagnosis and Therapy. 17th ed. Whitehouse Station, NJ: Merck Research Laboratories; 1999:285-292.

Blumenthal M, Goldberg A, Brinckmann J, eds. Herbal Medicine: Expanded Commission E Monographs. Boston, Mass: Integrative Medicine Communications; 2000:257.

Bovee-Oudenhoven IM, Wissink ML, Wouters JT, Van der Meer R. Dietary calcium phosphate stimulates intestinal lactobacilli and decreases the severity of a salmonella infection in rats. J Nutr. 1999;129:607-612.

Duncan SH, Flint HJ, Stewart CS. Inhibitory activity of gut bacteria against Escherichia coli 0157 mediated by dietary plant metabolites. FEMS Microbiol Lett. 1998;164:238-288.

Facey PC, Pascoe KO, Porter RB, Jones AD. Investigation of plants used in Jamaican folk medicine for anti-bacterial activity. J Pharm Pharmacol. 1999;51:1455-1460.

Fauci AS, Braunwald E, Isselbacher KJ, et al., eds. Harrison's Principles of Internal Medicine. 14th ed. Vol. 1. New York, NY: McGraw-Hill; 1998:796-801, 876-880, 904-905.

Fritsche KL, Shahbazian LM, Feng C, Berg JN. Dietary fish oil reduces survival and impairs bacterial clearance in C3H/Hen mice challenged with Listeria monocytogenes. Clin Sci. 1997;92:95-101.

Gabriel EP, Lindquist BL, Abud RL, Merrick JM, Lebenthal E. Effect of vitamin A deficiency on the adherence of fimbriated and nonfimbriated Salmonella typhimurium to isolated small intestinal enterocytes. J Ped Gastroenterol Nutr. 1990;10:530-535.

Gustafson JE, Liew YC, Chew S, Markham J, Bell HC, Wyllie SG, Warmington JR. Effects of tea tree oil on Escherichia coli. Letters in Applied Microbiology. 1998;26:194-198.

Hatchigian EA, Santon JE, Broitman SA, Vitale JJ. Vitamin A supplementation improves macrophage function and bacterial clearance during experimental Salmonella infection. PSEBM. 1989;191:47-54.

Haubrich WS, et al. Bockus Gastroenterology. 5th ed. Philadelphia, Pa: W.B. Saunders; 1995:1195-1210.

Hruby K, Csomos G, Fuhrmann M, Thaler H. Chemotherapy of Amanita phalloides poisoning with intravenous silibinin. Hum Exp Toxicol. 1983;2(2):183-195.

Jacobs J, Jiménez M, Malthouse S, Chapman E, Crothers D, Masuk M, Jonas WB. Homeopathic treatment of acute childhood diarrhea: results from a clinical trial in Nepal. J Altern Complement Med. 2000;6(2):131-139.

Jonas WB, Jacobs J. Healing with Homeopathy: The Doctors' Guide. New York, NY: Warner Books; 1996: 218-220.

Juven BJ, Kanner J, Schved F, Weisslowicz H. Factors that interact with the antibacterial action of thyme essential oil and its active constituents. J Appl Bacteriol. 1994;78:626-631.

Mandell GL, et al. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 4th ed. New York, NY: Churchill Livingstone; 1995:1012-1020.

Murray PR, et al. Manual of Clinical Microbiology. 7th ed. Washington, DC: ASM Press; 1999:356-359.

Rabbani GH, Butler T, Knight J, Sanyal SC, Alam K. Randomized controlled trial of berberine sulfate therapy for diarrhea due to enterotoxigenic Escherichia coli and Vibrio cholerae. J Infect Dis. 1987 May;155(5):979-984.

Rosen P, et al. Emergency Medicine: Concepts and Clinical Practice. 4th ed. Vol. 3. St. Louis, Mo: Mosby; 1998:1931-1938, 2513-2516, 2178-2179.

Sabeel AI, Kurkus J, Lindholm T. Intensive hemodialysis and hemoperfusion treatment of Amanita mushroom poisoning. Mycopathologia. 1995;131(2):107-114.

Taylor RB, et al. Family Medicine: Principles and Practice. 5th ed. New York, NY: Springer-Verlag; 1998:812-815.

Ullman D. Homeopathic Medicine for Children and Infants. New York, NY: Penguin Putnam; 1992: 75-77.

Ullman D. The Consumer's Guide to Homeopathy. New York, NY: Penguin Putnam; 1995: 243-245.

Verma RJ, Shalini M. Ochratoxin A-induced cytotoxicity to human red blood cells and its prevention by certain vitamins. Med Sci Res. 1997;25(12):833-834.

Yonekura K, Kawakita T, Mitsuyama M, Miura O, Yumioka E, Suzuki A, Nomoto K. Induction of colony-stimulating factor(s) after administration of a traditional Chinese medicine, xiao-chai-hu-tang (Japanese name: shosaiko-to). Immunopharmacol Immunotoxicol. 1990;12(4):647-667.

Yonekura K, Kawakita T, Saito Y, Suzuki A, Nomoto K. Augmentation of host resistance to Listeria monocytogenes infection by a traditional Chinese medicine, ren-shen-yang-rong-tang (Japanese name: ninjin-youei-to). Immunopharmacol Immunotoxicol. 1992;14(1-2):165-190.

Review Date: December 2000
Reviewed By: Participants in the review process include: Jacqueline A. Hart, MD, Department of Internal Medicine, Newton-Wellesley Hospital, Harvard University and Senior Medical Editor Integrative Medicine, Boston, MA; Leonard Wisneski, MD, FACP, George Washington University, Rockville, MD.

Copyright © 2004 A.D.A.M., Inc

The publisher does not accept any responsibility for the accuracy of the information or the consequences arising from the application, use, or misuse of any of the information contained herein, including any injury and/or damage to any person or property as a matter of product liability, negligence, or otherwise. No warranty, expressed or implied, is made in regard to the contents of this material. No claims or endorsements are made for any drugs or compounds currently marketed or in investigative use. This material is not intended as a guide to self-medication. The reader is advised to discuss the information provided here with a doctor, pharmacist, nurse, or other authorized healthcare practitioner and to check product information (including package inserts) regarding dosage, precautions, warnings, interactions, and contraindications before administering any drug, herb, or supplement discussed herein.

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