People have been eating oysters (oysters) for more than 2,000 years. These bivalve molluscs are filter feeders and consume approximately 25 gallons of water per day. While oysters support healthy shorelines and help keep water bodies clean, as filter feeders, they also contain pathogens that can make you sick.
According to the U.S. Centers for Disease Control and Prevention (CDC), nearly 80,000 people get sick each year from eating raw or undercooked oysters, and as many as 100 people die. Various Vibrio strains can cause illness, and signs and symptoms may appear within 24 to 48 hours after eating contaminated oysters. The severity of your condition may depend on the strain causing the infection.
If you experience stomach discomfort after eating oysters, you may be infected with Vibrio parahaemolyticus. This strain causes only minor infections, leading to side effects such as diarrhea and vomiting. The infection may be more severe if you eat oysters contaminated with Vibrio vulnificus . This strain of Vibrio can cause blood infections, skin blistering, amputation and even death.
No matter how severe your symptoms are, if you feel ill after eating raw oysters, you should contact your health care provider for an evaluation and treatment plan. Unfortunately, according to the CDC, there's no evidence that antibiotics can help infections, but in severe cases, antibiotics may be prescribed anyway.
Could it be an allergy?
Shellfish such as oysters are one of the most common food allergens. If you experience stomach upset after eating oysters, whether raw or cooked, it could be an allergic reaction. People of any age can be allergic to shellfish, but it's most common in adults.
An allergy is when the immune system overreacts to a substance that it believes is harmful, although for most people this is not the case. Symptoms of an allergic reaction usually appear within a few minutes to an hour after eating oysters. Your allergy symptoms may include:
- stomach ache
- swelling of lips, tongue, or throat
In severe cases, oyster allergy may cause anaphylaxis, a life-threatening condition that may result in shortness of breath or loss of consciousness and requires immediate medical attention. If you suspect you have an oyster allergy, talk to your doctor for a formal evaluation, diagnosis, and treatment plan.
Reduce risk of side effects
What you do if you get sick from oysters may depend on the underlying cause of your illness. For allergies, you need to eliminate oysters from your diet to prevent allergic reactions. Even if your initial side effects are mild, a more serious reaction can occur at any time.
It is impossible to tell by sight or smell whether an oyster is contaminated with pathogens. The CDC says the best way to reduce your risk of illness is to always cook oysters completely before eating them.
Be sure to discard any shelled molluscs before adding the oysters to the pot. To kill pathogens, cook oysters until their shells open, then cook for an additional three to five minutes. If you have shucked the oysters, you can safely eat the shellfish after boiling for three minutes. Always wash your hands with soap and water after handling oysters. Despite what friends and family say, hot sauce and lemon juice don't kill germs.
Oysters and food poisoning
According to a 2011 report from the Centers for Disease Control and Prevention, contaminated food, including oysters, sickens an estimated 48 million Americans each year. A variety of microorganisms can cause oyster food poisoning, including norovirus and Vibrio. Most people recover from the adverse symptoms of food poisoning within a few days. However, one strain of Vibrio can cause life-threatening illness in people with cancer, HIV or liver disease.
norovirus food poisoning
According to the U.S. Centers for Disease Control and Prevention (CDC), norovirus causes nearly 50 percent of food poisoning cases and is often associated with the consumption of contaminated fruits, green leafy vegetables, or shellfish such as oysters. The virus can also be spread through contact with contaminated surfaces or person-to-person contact. Symptoms such as nausea, vomiting, watery diarrhea and abdominal cramping usually appear within 12 to 48 hours of exposure. Healthy adults usually recover within 3 days without requiring medical attention.
Vibrio food poisoning
Vibrio bacteria that thrive in warm coastal waters, including the Gulf of Mexico, can contaminate oysters before they are harvested. Symptoms such as vomiting and non-bloody diarrhea may occur within 2 to 48 hours after eating raw oysters contaminated with Vibrio parahaemolyticus, which can last for 2 to 8 days. However, if the infection is caused by Vibrio vulnificus, similar symptoms usually appear within 1 to 7 days and can lead to more severe illness, especially in susceptible people.
Treatment of food poisoning caused by contaminated oysters usually focuses on replacing fluids and electrolytes lost through vomiting and diarrhea. For otherwise healthy people, eating a clear liquid diet and taking over-the-counter medications to control symptoms is usually enough to make a full recovery within a few days. Contact your doctor immediately if you notice bloody stools, fever and chills, or if your symptoms worsen or do not resolve.
People with cancer, HIV, liver disease, alcoholism, diabetes, and other causes of immune deficiency are at greater risk of developing sepsis or bloodstream infections from V. vulnificus infection. According to the 2013 publication "Safe Food Microbiology," the bacteria invade the bloodstream and cause death in about 40 to 60 percent of reported cases. Seek immediate medical attention hours to days after eating raw oysters.