Food poisoning can be caused by toxins although these are the least common cause. If this illness is caused by toxins then it is usually due to inadequate food preparation or poor choice of foods.

Note: when we say ‘poor choice of foods’ we are referring to wild mushrooms, berries etc. Many people enjoy foraging for these but if you considering doing this then make sure that you know which varieties to pick and which to leave well alone.

A toxin is defined as ‘a poisonous substance produced by a living organism’although it can also include ‘man-made’substances. Toxins are designed to cause harm to anyone or anything which comes into contact with them.

In regard to food poisoning: the types of toxins this guide deals with include:

Each subsection is discussed in detail within this section of the guide.

Many of the bacteria which cause food poisoning release toxins once they have penetrated cells within the human intestine. These toxins can spread within the gastrointestinal tract or travel to other parts of the body via the bloodstream.

Natural toxins

But as well as these toxins there are others, produced by certain types of foods, which are known to cause food poisoning. These foods contain ‘natural toxins’ which act as a form of protection for these foods against bacteria, strong sunlight and the weather.

In other cases, the toxin is a type of pesticide which helps to fight off insect attacks.

Foods which contain natural toxins include:

  • Courgettes
  • Red kidney beans
  • Seeds within certain fruits, e.g. apples or peaches
  • Rhubarb
  • Sweet potatoes/potatoes

Another group of toxins found in fish are ‘marine toxins’.

Marine toxins

These toxins are found in fish such as tuna, mackerel, prawns and oysters and are responsible for several types of food poisoning which include scombroid poisoning, ciguatera poisoning and neurotoxic poisoning.

These toxins are found within various seaweeds and algae or occur when fish starts to decompose (or has ‘gone off’).


These are often sprayed over crops in fields to protect them from insects, bacteria, parasites etc. Examples of these include fruits and vegetables.

However, they have been linked with some forms of bacteria which are known to cause food poisoning. These include the e coli, salmonella and listeria bacteria which often multiply after contact with pesticides.

Children appear to be a greater risk of poisoning from pesticides than adults which may be due to their greater exposure, for example handling and playing with soil; or because they are more vulnerable to the effects.

Find out more in our children and food poisoning section.

Food poisoning caused by toxins tends to be rare but it is useful to know what the risks are and how these can be prevented. Find out more within this section of this guide.

Food Poisoning Guide

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