Food poisoning occurs when you eat food contaminated with bacteria or other toxins. Symptoms include diarrhea, vomiting, and stomach cramps, and generally start 4 to 36 hours after eating contaminated food. While food poisoning is often caused by bacteria, it can also result from eating poisonous plants (some mushrooms, for instance) and animals (pufferfish). Food poisoning is especially common during summer when food may not be kept cold enough to prevent bacteria from growing.
Signs and Symptoms
The typical signs of food poisoning are nausea, vomiting, abdominal cramping, diarrhea, head or muscle aches, and fever. 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 and swallowing, paralysis that spreads downward, respiratory failure, and death
- Salmonella spp., Shigella spp., and Campylobacter jejuni (C. jejuni): fever, chills, and bloody diarrhea
- Escherichia coli (E. coli): hemorrhagic colitis (diarrhea with very little stool and large amounts of blood), occurring up to 3 days after eating contaminated food
- Mushroom poisoning: stomach upset, delirium (confusion), vision difficulties, heart muscle problems, kidney failure, death of liver tissue, and death if left untreated
Fish poisoning causes nausea, vomiting, diarrhea, abdominal pain, dizziness, and headache. Specific types of fish poisoning can cause other signs and symptoms, such as:
- Ciguatera (caused by toxins in some fish, including grouper, snapper, mackerel, and barracuda): 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
- 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, and death (Pufferfish poisoning).
- Numbness or tingling around the mouth or in the arms and legs, trouble swallowing, difficulty speaking (Shellfish poisoning, caused by toxins in algae that are eaten by shellfish) .
What Causes It?
Usually bacteria and algae cause food poisoning, but poisonous plants and animals are other potential causes.
Common bacterial causes include:
- E. coli in undercooked hamburger, unpasteurized apple juice or cider, raw milk, contaminated water (or ice), vegetables fertilized by cow manure, or spread from person to person
- 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 cool, moist foods (such as potato and egg salads) that are handled after cooking
- Staphylococcus aureus (S. aureus) in salad dressing, ham, eggs, custard-filled pastries, mayonnaise, and potato salad (usually from the hands of food handlers)
- C. jejuni in raw milk and chicken
- C. botulinum in improperly 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
- V. cholerae in bivalve (two shelled) shellfish (such as mussels, clams, oysters, and scallops), raw shellfish, and crustaceans (such as lobsters, shrimp, and crabs)
Common types of fish poisoning include:
- 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, shark) that have eaten toxic plankton
- Puffer fish poisoning from the organs and flesh of puffer fish
- Poisoning from shellfish that feed on certain algae
Mushroom poisoning occurs from eating poisonous wild mushrooms, especially Amanita phalloides.
Who's Most At Risk?
Infants and the elderly are at greater risk for food poisoning. Other risk factors include:
- A pre-existing medical condition, such as chronic kidney failure, liver disease, or diabetes
- Taking antibiotic, antihistamine, or steroid medicines
- Sickle cell anemia and other problems with red blood cells
- A weakened immune system, pregnant women and people over age 65 are most at risk
- Traveling in an area where contamination is more likely
Listeriosis is most common in pregnant women, fetuses, and people with immune problems. When a fetus is infected with listeria, it may be born prematurely or die.
What to Expect at Your Provider's Office
Your health care provider will examine you for signs and symptoms of food poisoning, such as stomach problems, and dehydration. Your health care provider may also ask about foods you have eaten recently, where you may have traveled, and if you have had contact with people showing similar symptoms. Tests of your vomit, blood, and stool can identify the cause. In the case of botulism, your health care provider may request electromyography (a test to measure electric impulses in the muscles) to confirm the diagnosis. A lumbar puncture (spinal tap) may be done to check for signs and symptoms related to central nervous system disorders.
These steps can help prevent food poisoning:
- Wash your hands and clean any dishes or utensils when you are making or serving food.
- Keep juices from meat, poultry, and seafood away from ready-to-eat foods.
- Cook foods to proper temperatures.
- 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.
- Do not feed honey to children under 1 year of age.
- Do not eat wild mushrooms.
- When traveling where contamination is more likely, eat only hot, freshly cooked food. Boil water before drinking. Do not eat raw vegetables or unpeeled fruit.
- Always refrigerate fish.
- Don't eat tropical fish caught during blooms of poison plankton.
- Eat pufferfish only in specially licensed restaurants with chefs trained to cook it.
- Don't eat shellfish exposed to red tides.
If others may 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 for most cases of food poisoning involve replacing fluids and electrolytes (such as sodium, potassium, magnesium, and chloride). While experiencing vomiting and diarrhea, the person should avoid solid food but increase clear liquids. In more severe cases, a person may need help either breathing or stopping vomiting. Health care providers usually don't prescribe antibiotics because they may prolong diarrhea. If you have eaten certain toxins (such as from mushrooms or shellfish), your health care provider may take steps to clean out your stomach (a process called lavage, or pumping the stomach) and administer activated charcoal, which can help absorb the remaining toxin.
Depending on the symptoms, cause, and severity of food poisoning, a health care provider may prescribe drugs, including:
- Oral rehydration therapy
- Antitoxin to neutralize toxins from C. botulinum (only given within the first 72 hours)
- Amitriptyline to control the numbness and tingling from ciguatera poisoning
- Apomorphine or ipecac syrup to cause vomiting and help rid the body of toxins
- Atropine for mushroom poisoning
- Diphenhydramine and cimetidine for fish poisoning
- Mannitol for nerve-related symptoms of ciguatera poisoning
Complementary and Alternative Therapies
If you are suffering from severe food poisoning, seek conventional medical treatment. Complementary and alternative therapies are best used to strengthen the body and aid in the prevention of food poisoning. Animal studies have shown that certain vitamins and nutrients may protect against some food toxins while others may actually worsen the effects of toxins. Milk thistle is an herb commonly used in Europe as a primary treatment for mushroom poisoning. Homeopathy may help treat 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).
- Take probiotics, such as Lactobacillus acidophilus and Lactobacillus bulgaricus, can help restore the balance of good bacteria in the intestine. If you are traveling to an area where the food and water may be contaminated, in addition to taking the precautions above, taking probiotics both before and during your trip may help maintain intestinal health. People with weakened immune systems should speak with their doctors before taking probiotics.
- Apple cider vinegar is a traditional remedy that, although it has not been studied scientifically, may have some antimicrobial properties. Mix 2 tsp. in one cup warm water and drink several times a day.
- Several studies suggest that a number of cooking herbs, including thyme, rosemary, basil, coriander, sage, spearmint, and fennel have strong antimicrobial effects against food borne pathogens, and may add an additional layer of protection when used in cooking.
For specific types of food poisoning:
- Alpha-lipoic acid -- Several reports indicate that alpha-lipoic acid, an antioxidant commonly found in broccoli, spinach, and beef, may help treat Amanita (mushroom) poisoning, especially when combined with milk thistle (Silybum marianum). Seek medical treatment if you suspect mushroom poisoning. Do not self-treat.
- Vitamin A -- Studies on rats show that vitamin A offers some protection against salmonella. Rats infected with Salmonella appeared to eliminate the bacteria from their bodies faster when pretreated with vitamin A rather than with placebo, according to one study. They also gained more weight and had a greater immune response than rats that didn't receive the vitamin.
- Calcium phosphate -- One animal study suggests that rats receiving calcium phosphate supplements may be protected from Salmonella poisoning. Researchers think calcium phosphate helps boost Lactobacillus, the good bacteria found in the intestine, which helps fight off Salmonella.
Supplements to avoid:
- 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 with Listeria infection should avoid foods containing fish oil.
Various herbs have been used traditionally to treat different types of food poisoning. More research is needed. The following herbs should not be used in place of conventional medical care and are listed only for the purposes of discussion.
Milk thistle (Silybum marianum) is often used for liver disorders and is widely used in Europe to treat Amanita mushroom poisoning. Studies show that patients with Amanita poisoning can be effectively treated with pharmaceutical 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 Listeria suggest they may be effective for food poisoning. Active ingredients include:
- Asian ginseng (Panax ginseng)
- Astragalus root (Astragalus membranaceus)
- Chinese cinnamon bark (Cinnamomum aromaticum)
- Ginger root (Zingiber officinale)
- Licorice ( Glycyrrhiza glabra)
- Peony root (Paeonia officinalis)
- Skullcap (Scutellaria lateriflora)
Seek the advice of a trained and licensed herbalist or practitioner of Traditional Chinese Medicine who will guide your individual treatment. Do not self-treat with herbs. Some herbs should not be taken if you have heart disease or high blood pressure, or if you take blood-thinning medication. In addition, some herbs interact with other herbs, supplements, and prescription medications, so it is important to make sure all your health care providers know what you are taking.
Laboratory (test tube) studies suggest that the following herbs have antibacterial or antimicrobial properties, although there is no evidence they are effective for treating food poisoning in humans. Do not use these herbs without speaking to a physician or knowledgeable herbal practitioner. Some side effects can be dangerous:
- Bittervine (Mikania micrantha)
- Goldenseal (Hydrastis canadensis)
- Oregon grape (Mahonia aquifolium)
- Chamomile (Matricaria recutita)
Barberry (Berberis vulgaris) has also been used traditionally to treat diarrhea from infectious causes such as E. coli and V. cholera. Berberine, the active ingredient in barberry, can cause brain damage in newborns. Speak to a physician before using berberine-containing herbs with children of any age.
Studies examining the effectiveness of homeopathic remedies for food poisoning are lacking. Before prescribing a remedy, homeopaths take into account a person's constitutional type -- your physical, emotional, and intellectual makeup. An experienced homeopath assesses all of these factors when determining the most appropriate remedy for a particular individual. Below are some more common remedies for food poisoning or diarrhea:
- 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. Practitioners may also recommend Arsenicum 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.
Most cases of food poisoning are mild and clear up on their own within 4 - 7 days. However, with mushroom poisoning, up to half of people may die. With botulism, less than 10% die, and some people may need help breathing for months afterward. More than half of poisonings from pufferfish are fatal. Death is rare in other fish poisonings, but nerve-related symptoms can continue for months.
The following are some possible after effects of food poisoning:
- After shigellosis, white blood cell problems and kidney problems
- After E. coli infection, kidney problems and bleeding problems
- After botulism, long hospital stays (1 - 10 months) with fatigue and difficulty breathing for 1- 2 years, or muscle weakness followed by respiratory failure
- After salmonellosis, Reiter syndrome (an arthritis-like disease) and inflammation of the heart lining
- After campylobacteriosis, Guillain-Barré syndrome (a nerve disease)
For a severe case of food poisoning, you may need to stay in the hospital to receive fluids and electrolytes, so health care providers can monitor your breathing. Doctors may need to insert a tube down the throat (intubate) or connect you 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.
Abubakar I, Irvine L, Aldus CF, et al. A systematic review of the clinical, public health and cost-effectiveness of rapid diagnostic tests for the detection and identification of bacterial intestinal pathogens in feces and food. Health Technol Assess. 2007;11(36):1-216.
Beers MH, Porter RS, et al. The Merck Manual of Diagnosis and Therapy. 18th ed. Whitehouse Station, NJ: Merck Research Laboratories; 2006:1642-1644.
Blumenthal M, Goldberg A, Brinckmann J, eds. Herbal Medicine: Expanded Commission E Monographs. Boston, MA: Integrative Medicine Communications; 2000:257.
Chan YC, Wiedmann M. Physiology and genetics of Listeria monocytogenes survival and growth at cold temperatures. Crit Rev Food Sci Nutr. 2009;49(3):237-253.
Ferri FF. Food poisoning, bacterial. Ferri's Clinical Advisor 2015. Philadelphia, PA: Elsevier Mosby; 2015:465-466.e2.
Irons R, Anderson MJ, Zhang M, Fritsche KL. Dietary fish oil impairs primary host resistance against Listeria monocytogenes more than the immunological memory response. J. Nutr. 2003;133:1163-1169.
Jackson BR, Griffin PM, Cole D, Walsh KA, Chai SJ. Outbreak-associated Salmonella enterica serotypes and food Commodities, United States, 1998-2008. Emerg Infect Dis. 2013;19(8):1239-1244.
Jacobs J, Jiménez-Pérez M, Malthouse S, et al. Homeopathic treatment of acute childhood diarrhea: results from a clinical trial in Nepal. J Altern Complement Med. 2000;6(2):131-139.
Lee MH, Kwon HA, Kwon DY, et al. Antibacterial activity of medicinal herb extracts against Salmonella. Int J Food Microbiol. 2006;111(3):270-275.
Lixandru B, Dracea N, Dragomirescu C, et al. Antimicrobial activity of plant essential oils against bacterial and fungal species involved in food poisoning and/or food decay. Roum Arch Microbiol Immunol. 2010;69(4):224-230.
Mody RK, Griffin PM. Foodborne Disease. In: BennettJE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:1283-1296.e3.
Pigott D. Foodborne illness. Emergency Medicine Clinics of North America. 2008:26(2)475-497.
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;155(5):979-984.
Steven D. Ehrlich, NMD, Solutions Acupuncture, a private practice specializing in complementary and alternative medicine, Phoenix, AZ. Review provided by VeriMed Healthcare Network. Also reviewed by the A.D.A.M. Editorial team.
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