Botulism Symptoms and Diagnosis

High angle view of cans filled with vegetables

Botulism is not actually an infection, but is an intoxication and is usually associated with consuming contaminated canned food. Botulism can start with unusual symptoms, such as a droopy eyelid, but it can progress and cause serious health problems, such as breathing difficulties.

Causes of Botulism

Botulinum toxin binds to the tiny space between a nerve and a muscle, preventing the nerve from sending a message to the corresponding muscle. When a nerve cannot send a message to direct a muscle to move, the muscle becomes paralyzed from botulism infection.

The bacteria can produce large amounts of botulinum toxin, which can then spread throughout the body, paralyzing many muscles at a time.

The bacteria that causes botulism can thrive in canned food. The bacteria live on the surface of uncooked fruit and vegetables, and they are less likely to survive if they are exposed to acidity or high heat.

In general, canned foods that are prepared at home without the use of safe processing methods are at highest risk. But there are also outbreaks of botulism related to professionally and industrially canned foods as well, although these outbreaks are few and far between.

When canned food is exposed to oxygen through a dent or a small hole in the can, this can also allow the bacteria to grow. If you have a can of food that appears damaged or has an irregular shape or shows signs or liquid bubbling or a bad smell, it is safest to discard the can and the food inside it, because eating the food can cause botulism or even another infectious type of food poisoning.

Signs and Symptoms 

Botulism is caused by a type of bacteria called Clostridium botulinum and may also be caused by related bacteria called Clostridium butyricum and Clostridium baratii. These bacteria produce a toxin called botulinum toxin that paralyzes certain muscles and nerves, causing any combination of the following signs and symptoms:

  • Droopy eyelid
  • Double vision
  • Blurred vision
  • Droopy face
  • Dry mouth
  • Slurred speech
  • Trouble swallowing
  • Muscle weakness
  • Trouble breathing
  • Chest palpitations

If you experience or observe the signs of botulism, you should seek medical attention immediately. The infectious bacteria that causes botulism releases a toxin that can rapidly cause dangerous paralysis, after which it is much more problematic and difficult to recover from. Untreated botulism can even be fatal.


Botulism is not a common medical condition, but if you experience face, eye or mouth weakness, your medical team will do a thorough physical examination to determine the cause of your weakness. You might need to have medical treatment started based on your doctors’ suspicion of botulism before the diagnosis is confirmed with a laboratory test. This is because the laboratory diagnosis of botulism takes several days, and treatment must be started sooner rather than later.

The Mouse Test 

A test that can help support or confirm the diagnosis of botulism is called the mouse inoculation test. The mouse inoculation test involves injecting a small amount of blood from a person who might have botulism into a mouse and also injecting a small amount of that person’s blood into another mouse that has already been vaccinated against botulism, to observe for effects. If only the un-vaccinated mouse shows signs of botulism, then the test points to the diagnosis of botulism.

Another description of the mouse inoculation test involves the injection of patient serum into a mouse and injection of antitoxin treated serum into another mouse to observe the difference in effects between the mice. If the mouse injected with regular serum shows signs of botulism, while the mouse injected with anti-toxin treated serum does not show signs, the test points to the diagnosis of botulism.

However, given that there is a 24-48 hour time window for mouse inoculation test effects to become apparent, if there is a strong suspicion of botulism, treatment with an antitoxin is started prior to test results. In the meantime, close observation of signs such as weakness and breathing ability is considered more valuable in directing your medical treatment and support.

Treatment of Botulism

There is no home treatment for botulism.

There are medications for botulism and there are treatments for the complications of botulism. The medication for botulism includes an antitoxin that counteracts effects of the bacterial infection. The antitoxin works by binding to the botulinum toxin, which is produced by the bacteria, and by preventing the toxin from paralyzing the muscles.

However, if you become infected and the botulism advances, with the toxin, actively acting on your muscles to paralyze them, then you may experience weakness. Depending on the severity of your weakness, you might need advanced medical interventions, such as breathing support with the assistance of a ventilator that helps move the air in and out of your body while you recover from the toxic infection.

Is Botulism the Same as Botox?

Yes, the same toxin that causes muscle paralysis from eating contaminated food is also deliberately used for cosmetic injections to temporarily prevent the appearance of wrinkles, to prevent migraine headaches and to relieve muscle stiffness. While it is not common, injections of botulinum toxin for medical or cosmetic reasons can cause unwanted paralysis of eye movement or facial muscles, which is usually temporary.

Wound Botulism

There is another type of botulism that causes similar symptoms but is not related to food poisoning. Wounds can also become infected with the bacteria, resulting in botulism. This is most common with IV drug use, and this type of botulism can also be treated with antitoxin and medical support for breathing.

A Word From Verywell

Most people have heard that it is unsafe to eat food from a dented or leaky can. Botulism is one of the types of food poisoning most associated with contaminated canned foods. It is important to discard damaged cans of food and to use safe methods when home canning food in order to prevent contamination.

If you suspect that you or someone else may have signs of botulism, it is important to seek medical attention immediately.

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Article Sources
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  • Clostridium, Peptostreptococcus, Bacteroides, and Other Anaerobes. In: Ryan KJ, Ray C. eds. Sherris Medical Microbiology, 6e New York, NY: McGraw-Hill; 2014.
  • Home-Canned Foods. Protect Yourself From Botulism.