Symptoms and Complications
Almost all forms of food poisoning produce nausea, vomiting, abdominal cramps, and diarrhea. The bacterial causes of food poisoning tend to cause these symptoms as well as fever and headache. Symptoms can start within hours to days after eating the contaminated food and last from a day to a week.
Many non-infectious (not caused by bacteria and their toxins, viruses, etc) forms of food poisoning affect the central nervous system and cause symptoms typical of nerve poisons.
Eating shellfish contaminated with saxitoxin, for example, will produce weakness or paralysis around the mouth in a few minutes, which slowly spreads to the rest of the body.
Signs of ciguatera poisoning include face pain, headache, itching, and odd sensations of alternating hot and cold.
Scombroid (histamine) fish poisoning causes the symptoms of excess histamine. Flushing, skin rash, and pain from overstimulation of affected organs, namely the stomach and intestines, appear within a few minutes.
Mushroom poisoning also attacks the nervous system. Shrunken eye pupils, tears, salivation or frothing at the mouth, sweating, vertigo, confusion, coma, and sometimes seizures appear within 2 hours of eating a poisonous mushroom. Insecticides based on organophosphates cause very similar symptoms. They're likely to be milder, since it is extremely rare for really large doses of insecticide to be eaten accidentally.
The most common complication of food poisoning is dehydration, when your body loses too much water and electrolytes (e.g., sodium, potassium). Food poisoning caused by the bacteria Listeria can cause problems for unborn babies, and E. coli infection can cause problems with the kidneys. Other complications can include arthritis and bleeding problems. Non-infectious food poisoning can occasionally lead to permanent nervous system problems and even death.
Making the Diagnosis
For food poisoning caused by bacteria, viruses, and parasites, a diagnosis can usually be made based on symptoms and a physical examination. Your doctor may order blood tests to check for dehydration or ask for a stool sample to check for bacteria or parasites.
For other types of food poisoning, getting the right diagnosis early can be vital. Some poisons have specific antitoxins that will cure the poisoning completely.
When people are poisoned in groups, it is usually easier to pinpoint the cause. Often, there's only one food that all the sick people ate, and this can be studied to determine the culprit.
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Treatment and Prevention
The treatment of food poisoning depends on the cause and on its severity.
For most people, food poisoning resolves quickly without treatment. For people with mild diarrhea lasting less than 24 hours, treatment should consist of drinking clear fluids such as oral replacement solutions. These solutions contain the right balance of water, salts, and sugar needed to prevent or treat mild dehydration. A solution can be made by mixing 1 teaspoonful of salt and 4 heaping teaspoonfuls of sugar with 1 liter of water.
It may be best to stay away from solid food during diarrhea and vomiting. Once you are able to take fluids, gradually start eating plain foods as tolerated. Avoid alcohol and caffeine while you are sick. People with severe symptoms or severe dehydration may need to be admitted to the hospital so they can receive rehydration solutions intravenously (into a vein).
Most bacterial food poisonings do not need antibiotics, but some types of infections may need antibiotic treatment.
For food poisonings that cause nervous system effects, there may be other medications or antidotes that can be used. For example, in mushroom (muscarine) poisoning, a medication called atropine* can be used to counter toxic effects. Poisonings with mushrooms and pesticides may also require stomach pumping (gastric lavage). Gastric lavage is a technique used in the hospital in which a tube is inserted from the mouth to the stomach and the stomach is pumped clean with liquids.
If poisoning is very severe, a patient may require a ventilator (artificial breathing machine), kidney dialysis, and or admission to a hospital intensive care unit.
You can't always prevent food poisoning, but there are some things that you can do to minimize your risk. The following are some tips:
- Wash your hands thoroughly with soap and warm water for at least 20 seconds before and after handling food, and after using the bathroom, changing diapers, or touching animals.
- If you have a skin infection like impetigo (Staphylococcus bacteria), don't prepare food for others while spots or sores are visible.
- Try to keep different foods and food types separate during preparation and storage.
- Use a separate cutting board and knife for raw foods and cooked foods.
- When reheating food, cook it thoroughly enough that the core reaches at least 170°F (or 75°C). This won't remove all poisons or kill all bacteria, but it helps against some common kinds.
- Be aware that some foods are more prone to causing food poisoning than others, which means you have to handle them more carefully. Green vegetables and carrots, for example, are less likely to be toxic than fish, meat, poultry, eggs, and dairy.
- Thoroughly cook meat and poultry, ensuring that recommended internal temperatures are reached.
- If you're keeping leftovers, refrigerate them as soon as possible. Do not let them sit out for longer than one hour or cool to room temperature.
- Do not thaw foods at room temperature – put them in the refrigerator for thawing.
- Throw out foods that could be contaminated. 2 days is usually the maximum that prepared foods should be stored in the refrigerator. Otherwise, they should be frozen.
- Keep cold foods cold and hot foods hot.
- Don't let kids lick the spoon if raw eggs are an ingredient.
*All medications have both common (generic) and brand names. The brand name is what a specific manufacturer calls the product (e.g., Tylenol®). The common name is the medical name for the medication (e.g., acetaminophen). A medication may have many brand names, but only one common name. This article lists medications by their common names. For information on a given medication, check our Drug Information database. For more information on brand names, speak with your doctor or pharmacist.
Jeffrey Heit, MD, Internist with special emphasis on preventive health, fitness and nutrition, Philadelphia VA Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.