Botulism is a rare but potentially fatal condition caused by toxins produced by Clostridium botulinum bacteria.

The toxins produced by C. botulinum are some of the most powerful toxins known to science. They attack the nervous system (nerves, brain and spinal cord) and cause paralysis (muscle weakness) that gradually spreads down the body from the head to the legs.

Other symptoms of botulism can include:

• blurred or double vision
• drooping eyelids
• difficulty swallowing (dysphagia)
• difficulty speaking (dysarthria)

If the condition is not treated quickly, the paralysis will eventually affect the muscles controlling breathing. This can cause fatal respiratory failure in up to one in every 10 people with the condition.

Botulism is a serious condition requiring immediate medical attention. Dial 999 for an ambulance if you or someone you know has symptoms of botulism.

Read more about the symptoms of botulism.

What causes botulism?

Botulism is caused by the bacteria Clostridium botulinum, found in soil, dust and river or sea sediments. The bacteria themselves are not harmful, but they can produce highly poisonous toxins when they are deprived of oxygen (such as in closed cans or bottles, stagnant soil or mud, or occasionally the human body).

There are three main types of botulism, which have slightly different causes:

• food-borne botulism can occur when someone eats food that is contaminated with infected soil if the food has not been properly canned, preserved or cooked
• wound botulism can occur when a wound becomes infected with the C. botulinum bacteria, it is usually caused by injecting illegal drugs contaminated with the bacteria, such as heroin, into muscle rather than a vein
• infant botulism can occur when a baby ingests spores of the C. botulinum bacteria in contaminated soil or food, such as honey

All these types of botulism are rare in the UK, although wound botulism has been by far the most common in the last 15 years or so.

In England and Wales since 2000, there have been 147 cases of wound botulism (eight deaths), but only seven cases of food-borne botulism (one death) and 11 cases of infant botulism (no deaths).

Read more about the causes of botulism.

Identifying and treating botulism

As botulism is a potentially life-threatening condition, it is usually diagnosed following admission to hospital.

A diagnosis is mainly based on your symptoms, although tests will be carried out on a sample of blood, faeces (stool), stomach contents, food, pus or tissue to detect the C. botulinum bacteria or toxin in order to confirm the diagnosis.

However, as treatment is most effective when given quickly, it will usually begin before the test results come back.

The way in which the condition is treated depends on the type of botulism you have, but treatment will usually involve neutralising the toxins with injections of special antibodies while the functions of the body (such as breathing) are supported.

Treatment will not reverse paralysis already caused by the toxin, but in most people any paralysis will improve naturally over the following weeks or months.

Read more about how botulism is treated.

Preventing botulism

Due to high standards of food hygiene in the UK, the chances of getting food-borne botulism from food bought in this country are virtually nil.

There is a slightly higher risk if you produce your own food, particularly if this involves canning. However, following food hygiene procedures and canning recommendations will reduce any risk.

You should also avoid eating food from visibly bulging or damaged cans, foul-smelling preserved foods, foods stored at the incorrect temperature and out of date foods.

Heroin users should avoid injecting heroin into their muscles. Injecting heroin into a vein or smoking can reduce the risk of botulism, although not using heroin at all is by far the best course of action. Read more about getting help to stop using heroin.

The specific cause is not identified in many cases of infant botulism, so it may not always be possible to prevent it. However, you should avoid giving honey to babies less than 12 months old because it has been known to contain C. botulinum spores.