What You Need to Know About Botulism and Canned Foods

What You Need to Know About Botulism and Canned Foods

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Stephanie Smith, Consumer Food Safety Specialist and Assistant Professor, Youth and Families Program Unit, Washington State University, Rachel Beck, Assistant, Youth and Families Program Unit, Washington State University
Though foodborne botulism is rare, it is deadly serious. Most cases of foodborne botulism are the result of eating improperly processed home-canned foods. This publication provides basic facts and tips for preventing botulism.
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There were 52 reported cases of foodborne botulism between 1985–2014 in Washington State (WSDH 2016a; 2016b). Although foodborne botulism is rare, the illness is very serious and can result in death. Botulism is caused by eating foods that are contaminated with the botulinum (botulism) toxin, which is produced by a bacterium called Clostridium botulinum (CDC 2016a). Most cases of foodborne botulism are the result of eating home-canned foods that have been improperly canned. This publication supplies basic facts on how you can prevent botulism.


Botulinum toxin is produced by a bacteria called Clostridium botulinum. C. botulinum is unable to grow in foods that have a high acid content, such as most fruits, or when exposed to oxygen. Therefore, the bacteria and toxin are most often associated with home-canned foods with low acid content, such as vegetables and meats, that have not been properly processed (Figure 1). In recent years, botulism outbreaks have occurred due to mishandling of other foods such as unrefrigerated homemade foods including salsa, garlic and herbs in oil, and foil-wrapped potatoes. Botulism is also associated with traditionally prepared salted or fermented seafood. Consuming very small amounts, even a small taste, can result in severe illness or death. Illness can occur within a period of a few hours or up to 10 days after eating food containing the botulism toxin. Symptoms may include double or blurred vision, drooping eyelids, slurred speech, difficulty swallowing, dry mouth, and increasing muscle weakness

Figure 1. Canned food.
usually affecting the upper part of the body initially, with subsequent progression down to the legs. Ingestion of the toxin can lead to paralysis of respiratory muscles resulting in death. If you have any of these symptoms, especially after eating home-canned food, go to a hospital immediately and inform the medical staff of the botulism concern.

Protect Yourself!

  • Use ONLY current, researched, and approved published recipes. Follow the guidelines for home canning provided in the USDA’s Complete Guide to Home Canning. For more information, on approved recipes and guidelines, contact your local Extension office. Use the appropriate canner for the recipe and follow all specified home canning processing times and recipes exactly (CDC 2016).
  • NEVER fill hot food into the jar in order to let the seal form without processing. You MUST use the appropriate canner/canning method to process the food safely (Figure 2). Canned foods at risk for botulism must be processed in a pressure canner at a specific temperature and for a specific length of time to ensure safety.
Figure 2. Never pour hot food into jars and let them sit to self-seal without also processing in the appropriate canner.
  • Do NOT open, smell, touch, or eat any food from jars that are damaged, cracked, leaking, swollen, squirt liquid or foam when opened, or look or smell bad. If you are ever unsure whether food is safe or not, ALWAYS throw it away.
  • Boil home-processed, low acid foods like tomato sauces, meats, soups and vegetables for 10 minutes in a saucepan before serving even if there is no sign of spoilage. Botulism toxin can be present in canned foods even if there are no signs, such as a leaking or swollen lid. If there are signs of spoilage, DO NOT eat the food. Throw it away.


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Issued by Washington State University Extension and the U.S. Department of Agriculture in furtherance of the Acts of May 8 and June 30, 1914. Extension programs and policies are consistent with federal and state laws and regulations on nondiscrimination regarding race, sex, religion, age, color, creed, and national or ethnic origin; physical, mental, or sensory disability; marital status or sexual orientation; and status as a Vietnam-era or disabled veteran. Evidence of noncompliance may be reported through your local WSU Extension office. Trade names have been used to simplify information; no endorsement is intended.