Food Intolerance Explained


What is a Food Intolerance?


Food intolerance is much more common than food allergy with a rapid increase in diagnosed and suspected cases over recent years. It is a hypersensitivity that does not involve the immune system and can be broadly categorised as enzymatic, pharmacological or an undefined reaction. People who suffer with a food intolerance have difficulty in digesting food or have a reaction when the body is exposed to naturally occurring chemicals and additives found in food. The same naturally occurring chemicals and additives can be found in a wide range of food that seem unrelated, but contribute to the overall daily dose.  


The onset of symptoms is usually longer and may be delayed by hours or even days after consuming food1. Although, the symptoms of an intolerance to histamine can occur within 30 minutes. Food intolerance is not life threatening, and common symptoms include stomach pain, bloating, diarrhoea, flatulence, skin rashes and itching2.



Pharmacological Factors


Pharmacological food intolerance is a reaction to chemicals that occur naturally in certain foods and include histamine, tyramine, serotonin caffeine and phenylethylamine. These chemicals are usually pharmacologically active if they are consumed in large quantities. They can be found in fish (histamine), cheese (tyramine), chocolate (phenylethylamine), serotonin (bananas) and caffeine (coffee)3. Common symptoms include diarrhoea and vomiting.



Undefined Factors


Undefined food intolerance is pseudo-allergic reaction to food additives and symptoms are like those of an allergic reaction3. Food additives include flavourings, preservatives (sulphites), anti-oxidants and emulsifiers. Known symptoms include asthma, rhinitis, itchiness and migraines.



Lactose intolerance


Lactose is the most common enzymatic food intolerance and affects more than 70% of the world’s population, especially those of Asian ethnicity. Problems arise when the body cannot produce enough lactase to digest a type of sugar found in milk called lactose. Lactase is an enzyme normally produced by cells lining the small intestine. They break down the lactose in glucose and galacose (other types of sugar) which are then absorbed into the bloodstream1. Problems arise when unabsorbed lactose moves down to the colon (large intestine). Bacteria ineffectively breaks down the lactose, resulting in the production of fatty acids and gases (carbon dioxide, hydrogen and methane)1. These acids and gases in the body result in common symptoms such as flatulence and bloating.



Food intolerance is a topic discussed on all our food safety, food allergy awareness and HACCP training courses. We are currently running Level 4 Food Safety and HACCP, and Level 3 Allergen Management courses in Milton Keynes. Percipio Training can also deliver any course onsite at your premises. Contact us now to find out more.



  1. Allergy UK (2018). Common Food Intolerances [Online]. Available at: [Accessed on 8 February 2018]
  2. NHS(2016). Lactose Intolerance. [Online]. Available at: [Accessed on 8 February 2018]
  3. Swiss Allergy Centre (2017) Food Intolerance. [Online]. Available at [Accessed on 8 February 2018]
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