Unexpected Sources of Botulism: What to Know and How to Spot the Symptoms

Most people know to be cautious with expired food or dented cans. But some foods that seem harmless can also create the perfect environment for a dangerous toxin to grow.

Botulism poisoning is rare, but it can become life threatening quickly. Understanding where it comes from and how to recognize the symptoms can help you act fast if exposure happens.

Botulism is a serious illness caused by a toxin made by the bacteria Clostridium botulinum. The toxin attacks the nerves and can cause muscle weakness, trouble breathing and paralysis. “Botulism is uncommon, but when it occurs, it’s considered a medical emergency,” says Alex Teshon, MD, a second-year medical toxicology fellow with Lehigh Valley Health Network, part of Jefferson Health.

There are several types of botulism, but foodborne botulism is one of the most well-known. It happens when someone eats food contaminated with the toxin. Infant botulism can also occur when babies younger than 1 year old ingest bacterial spores, which is why honey should never be given to infants.

Improperly canned foods are one of the most common sources of botulism, especially home-canned vegetables, meats and seafood. But experts say there are other foods people may not realize can become risky under certain conditions. 

• Foil-wrapped baked potatoes left at room temperature can create a low-oxygen environment where Clostridium botulinum can grow
• Garlic stored in oil at room temperature can also create a low-oxygen environment that allows  bacteria to grow
• Improperly canned foods that are low in acid, like green beans, corn, beets and meats, carry a high risk of carrying bacteria
• Honey contains bacteria spores that are safe for older children and adults, but are harmful to the digestive systems of infants under 1 year old

Symptoms of botulism can begin hours to days after exposure. One classic way clinicians remember the early neurological symptoms is with the “four D’s”:

• Dysarthria, slurred speech
• Diplopia, double vision
• Dysphonia, hoarseness or trouble speaking
• Dysphagia, difficulty swallowing

Other symptoms may include:

• Drooping eyelids
• Blurred vision
• Dry mouth
• Muscle weakness
• Difficulty breathing
• Paralysis

“Foodborne botulism may also cause gastrointestinal symptoms before neurological symptoms appear, including nausea, vomiting, diarrhea and abdominal cramps,” Dr. Teshon says.

In infants, symptoms may include constipation, a weak cry, poor feeding, trouble breathing and floppiness or weakness.

Botulism is a medical emergency. Anyone with symptoms, especially trouble swallowing, speaking or breathing, should seek immediate medical attention.

Doctors diagnose botulism based on symptoms, physical examination and laboratory testing. Treatment often includes an antitoxin that can help stop the toxin from causing further damage. Some people may require hospitalization or breathing support while the nerves recover.

“The earlier botulism is identified, the better the chances of preventing severe complications,” Dr. Teshon says. “If someone develops neurological symptoms after eating a potentially contaminated food, they should seek care right away.”

Fortunately, botulism is preventable in many cases. Simple food-safety steps can go a long way.

To reduce your risk:

• Refrigerate leftovers promptly.
• Keep foil-wrapped baked potatoes hot, or if you want to serve later, loosen the foil to allow for air circulation, and refrigerate to 40 degrees or colder.
• Refrigerate homemade garlic-in-oil mixtures and throw away after four days.
• Follow proper home-canning guidelines.
• Throw away bulging or damaged cans.
• Never give honey to babies younger than 1 year old.

While botulism is rare, knowing the warning signs and the surprising foods that can sometimes cause it can help keep you and your family safe.