Botulism

Botulism is a rare but serious condition caused by a spore-producing bacteria, Clostridium botulinum. The bacteria produce a toxin which can cause nerve damage.

Botulism occurs in three main forms:

  • Foodborne botulism is caused by eating or drinking foods that contain the botulism toxin.
  • Wound botulism occurs when bacteria enter a cut and produce the toxin. People who inject drugs are at increased risk of this form of botulism.
  • Intestinal botulism occurs when food contaminated with toxin-producing bacteria is consumed. The bacteria grow and produce the toxin in the intestines. The most common form is infant botulism, in children from six weeks to six months of age. Adults with altered gut flora (e.g., due to antibiotic use) or underlying intestinal disease can also develop intestinal botulism.

Other forms of botulism include inhalational and iatrogenic:

  • Iatrogenic botulism is a form of botulism that is caused by the accidental overdose of the botulism toxin that is injected for cosmetic or therapeutic use.
  • Inhalational botulism is unlikely, but it is possible if a person inhales the botulism toxin released in the air.

For foodborne botulism, symptoms usually appear 12 to 36 hours after ingesting contaminated food or drink but could appear as early as 6 hours or as long as 10 days after ingestion. For wound botulism, symptoms generally appear within 4 to 14 days. The incubation periods for intestinal colonization cases are estimated to be 30 days for infants but is unknown for adults. The time between exposure and developing iatrogenic botulism is reported to be 0 to 12 days.

Early symptoms may include fatigue, weakness, dizziness, or headache, followed by:

  • Vomiting and/or diarrhea (foodborne botulism)
  • Double vision or blurred vision
  • Drooping eyelids
  • Dry mouth or dry throat
  • Difficulty swallowing and speaking
  • Difficulty breathing
  • Paralysis

You can get foodborne botulism by eating food or drink contaminated with the botulism toxin. Foodborne botulism occurs when Clostridium botulinum bacteria grow and produce the toxin in food or drink that has not been sufficiently heated or cooked to inactivate the toxin.

The harmful bacteria grow and produce the toxin in conditions with little oxygen (anaerobic), low acidity (pH > 4.6), low salt, and sugar concentrations, and when stored at improper temperatures (>4°C), i.e., not kept refrigerated. For example, foodborne botulism has occurred when foods are improperly home-canned.

Poisonings have been commonly associated with lightly preserved foods such as fermented, salted, or smoked fish and meat products, and inadequately processed canned or bottled low-acid vegetables such as carrots, green beans, corn, and beets.

There have been no documented cases of person-to-person spread of botulism.

All forms of botulism can be fatal and require urgent medical attention. If you suspect that you may have botulism, seek medical attention right away.

Botulism is diagnosed through laboratory testing including blood tests or testing of body fluids. A wound swab is collected for wound botulism.

Botulism can be treated with an antidote (botulism antitoxin) if diagnosed early. Antitoxin can reduce the chances of complications. If you suspect you may have botulism, your doctor, in consultation with Toronto Public Health, will determine if you require the botulism antitoxin injection. If food has recently been eaten, sometimes clearing out the digestive system by removing undigested food from the stomach and giving medications to induce bowel movements is recommended.

To protect yourself and your family:

  • Refrigerate all foods labeled “keep refrigerated”.
  • Never eat food from cans that are leaking or have bulging ends.
  • Do not feed honey (even pasteurized honey) to children under one year old.
  • Do not taste food you think is spoiled.
  • Do not eat foods past their expiry date.
  • Practice safe home canning techniques:
    • Be sure to preserve all low-acid foods (e.g., carrots, green beans) in a pressure canner and follow the manufacturer’s instructions carefully.
    • Keep all work surfaces, food, utensils, equipment, and hands clean throughout the canning process.
    • Date and label preserves and canned goods.
    • Keep home-prepared foods stored in oil (e.g., garlic) in the refrigerator. Discard after one week. Use only fresh ingredients (e.g., herbs and vegetables).
    • To kill the toxin, boil all home-canned, low-acid foods for 10 minutes before eating them.
    • For home canning safety tips, see the Government of Canada’s Home canning safety fact sheet.
  • Drink homemade low-acid juices such as carrot juice immediately upon preparation.

Call Toronto Public Health at 416-338-7600 (TTY at 416-392-0658) or speak to your health care provider. You can also call 811 to connect to a registered nurse day or night for free, secure and confidential health advice.
Date modified: June 15, 2026