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Ohio State University Extension Fact Sheet

Family and Consumer Sciences

1787 Neil Avenue, Columbus, Ohio 43210-1295


What you don't see can hurt you


Barbara Rohrs


What is Botulism?

Botulism is the name of the food poisoning we get consuming the toxin of Clostridium botulinium. Botulism was formerly known as "Kerner's Disease." It was named after the man who signed the death certificate of people who ate contaminated sausage and died in an outbreak in Germany. In fact, botulism comes from the Latin word, botulus, which means sausage. Botulism is a rare but serious foodborne disease. It can be fatal. There are two different types of botulism poisoning that we need to be concerned with - adult and infant botulism.

The symptoms of botulism include difficulty in swallowing, speech and breathing, and double vision. The onset of botulism is usually 18 to 36 hours after eating the contaminated food, although it can be as soon as four hours and as long as eight days.

Where does botulism come from?

C. botulinum is found in soil all over the world. The bacteria have the ability to form a spore that is very resistant to heat and chemicals. The bacteria grow best anaerobically. That means it will grow in the absence of air. The spores formed in the absence of air produce a toxin. This toxin is the most deadly we know.

How can botulism be prevented?

There are very few cases of botulism each year. The death rate is high if not treated immediately. Prevention is extremely important. Home canning should follow strict hygienic recommendations to reduce risks. Pressure canners should be used for all low-acid foods. In addition, home-canned foods should be boiled for 20 minutes before eating. The botulism spores can only be killed by the high heat which can be obtained in a pressure canner. The toxin (that is produced in anaerobic conditions) can only be destroyed by boiling.

Are home-canned foods the only concern?

Infant botulism is a concern for children under one year of age. It is possible for bees to pick up the botulism spores from flowers or soil. These spores are not destroyed during the processing for honey. The botulism spores grow in the baby's intestinal tract and then produce the toxin. After the age of one year, this no longer happens because of higher acid levels in the baby's tummy.

Flavored oils can be a concern if not prepared correctly. When herbs, garlic, or tomatoes are placed in oils, the botulism spores on the plant material can start to produce the toxin in this anaerobic (oxygenless) mixture. To be safe, keep these flavored oils refrigerated and make only the amount of herbal oils and butters that will be used in a few days. Using dried herbs and vegetables will also reduce the risk.

Baked potatoes wrapped in foil and kept at room temperature can also form the anaerobic conditions the botulism spores need to produce their toxin. For this reason, leftover potatoes should be refrigerated. Potato salad made from leftover baked potatoes has been implicated in botulism poisoning.

What precautions should I take?

  1. Boil all home-canned, low-acid foods 20 minutes before eating
  2. Discard all raw or canned food that shows any sign of being spoiled.
  3. Discard all bulging or swollen cans of food and food from glass jars with bulging lids.
  4. DO NOT TASTE food from swollen containers or food that is foamy or has a bad odor.
  5. Process low-acid foods at temperatures above boiling (which can only occur under pressure) and for the recommended time for the size of can or jar you are using.
  6. Can low-acid foods in a pressure canner. Do not can low-acid foods in the oven, in water-bath, open kettle or vegetable cooker.
  7. Clean all surfaces with chlorine/water solution (one tablespoon of bleach per gallon of water) that leaky containers may have contaminated . Then discard any sponges or cloths used for cleanup.
  8. Do not give honey or foods with honey to infants under one year of age.



1. National Center for Disease Control, Center for Disease Control and Prevention

2. U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Foodborne Pathogenic Microorganisms and Natural Toxins Handbook, The Bad Bug Book.

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