Food Poisoning

  • Medical Author:
    Benjamin Wedro, MD, FACEP, FAAEM

    Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

  • Medical Editor: Charles Patrick Davis, MD, PhD
    Charles Patrick Davis, MD, PhD

    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

Food Poisoning Dangers Slideshow

Quick GuideFood Poisoning Pictures Slideshow: 20 Common and Uncommon Types, Signs and Symptoms

Food Poisoning Pictures Slideshow: 20 Common and Uncommon Types, Signs and Symptoms

When should the doctor be called for food poisoning?

With a clear fluid diet and rest, most infections resolve on their own within 24 hours. A health-care professional should be contacted if the vomiting and diarrhea are associated with one or more of the following symptoms:

  • fever,
  • blood in the stools,
  • signs of dehydration including lightheadedness when standing, weakness, decreased urination,
  • diarrhea that lasts longer than 72 hours, and/or
  • repeated vomiting that prevents drinking and rehydrating (replacing the fluids lost due to fever, diarrhea, and vomiting).

How is food poisoning diagnosed?

Most times, the diagnosis of food poisoning is made by history and physical examination. Often, the patient volunteers the diagnosis when they come for medical care. For example, "I got sick after eating potato salad at a picnic," or, "I drank a raw egg protein shake."

The health-careprofessional may ask questions about the symptoms, when they started, and how long they have lasted. A review of systems may help give direction as to what type of infection is present. For example, a patient with numbness of their feet and weakness may be asked about whether they have opened any home canned food recently.

Travel history may be helpful to see if the patient had been camping near a stream or lake and the potential for drinking contaminated water, or if they have travelled out of the country recently and have eaten different foods than they normally do, such as raw eggs or wild game.

Physical examination begins with taking the vital signs of the patient (blood pressure, pulse rate, and temperature). Clinical signs of dehydration include dry, tenting skin, sunken eyes, dry mouth, and lack of sweat in the armpits and groin. In infants, in addition to the above, subtle signs of dehydration may include poor muscle tone, poor suckling, and sunken fontanelle.

Routine blood tests are not usually ordered unless there is concern about something more than the vomiting and diarrhea. In patients with significant dehydration, the health-careprofessional may want to check electrolyte levels in the blood as well as kidney function. If there is concern about hemolytic uremic syndrome, a complete blood count (hemogram, CBC) to check the red blood cells, white blood cells, and platelet count may be ordered. If there is concern about hepatitis, liver function tests may be ordered.

Stool samples may be useful especially if there is concern about infections caused by Salmonella, Shigella, and Campylobacter, the common non traveler's diarrhea. This is especially true when the patient presents with bloody diarrhea, thought to be due to infection. If there is concern about a parasite infection, stool samples can be examined also for the presence of parasites. Some parasites may be very difficult to see under the microscope, including Cyclospora, because it is so tiny.

Depending on the suspected cause of the food poisoning, there are some immunological tests (for example, detection of Shiga toxins) that the CDC recommends. Cyclospora DNA may be detected in the stool using molecular testing called polymerase chain reaction (PCR). Other methods may be used (for example, detection of prions in tissue samples).

Medically Reviewed by a Doctor on 8/31/2015
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