Common Food Intolerances

Food is the primary source of nutrients that is required to facilitate the body to perform its function but if some food is making you sick it could be more than an allergy. Studies suggested that about 20%of the population is affected by food intolerance.1

People with food intolerance are unable to digest a certain amount of food due to a lack of

enzymes or a food sensitivity that causes unpleasant symptoms after eating a specific amount

of Food. Most common food intolerances are caused by lactose, casein that are present in milk, and casein that is found in dairy products. Food tolerance can cause adverse reactions if symptoms are not properly managed.2

What is a food intolerance

Food intolerance is a non-immunological response in which the body produces a pharmacological response after eating food that the body is unable to digest due to a lack of enzymes that aid in the digestion process and produce uncomfortable symptoms.

Symptoms may develop after a few hours of eating and may persist for some days but a small amount of that food does not produce any adverse reaction.

People who have stomach problems are more prone to develop food intolerance.3

Symptoms of a food intolerance

The severity of symptoms depends on the amount of food consumed but symptoms appear gradually in a few hours and remain for several days. People with food intolerance have experience symptoms such as :

  • Stomach discomfort
  • Bloating
  • Diarrhea
  • Spasms 
  • Nausea
  • Headache
  • Heartburn
  • Irritable Bowel Syndrome
  • Joint pain4

Intolerance vs allergy

For proper treatment diagnosis is important but food intolerance is often confused with a food allergy because of their similar symptoms of food sensitivity.

  • Food allergy is an immune-mediated response due to the activation of IgE antibodies but in food intolerance, the digestive system is affected
  • The allergic symptom appears in food allergies like rash, chest pain, hives, and shortness of breath whereas, food intolerance involves gastric symptoms including bloating, cramps, heartburn, and irritability
  • Food allergy is triggered by a small amount of food but symptoms of food intolerance appear after taking a certain amount of food
  • Food allergies are not reversible and can produce life-threatening effects but food intolerance does not produce life-threatening conditions and is easily avoidable
  • Food allergy symptoms instantly appear after getting exposed to the allergic substance but food intolerance symptoms appear slowly
  • Allergic reactions appear every time in food allergy but that is not necessary with food intolerance5

Causes of food intolerances

Causes of Food intolerance are different for every person which includes:

  • Metabolism problem: Most people develop food intolerance due to a deficiency of the enzymes that are needed for the digestion of food such as Lactose intolerance
  • Gastrointestinal Diseases: People with Inflammatory Bowel Disease(IBD), Celiac Disease, and Stress related conditions are affected by any food sensitivity
  • Sensitivity with Active Pharmaceutical Ingredient: The presence of a pharmacologically active substance in the food also triggers food intolerance symptoms
  • Preservatives: The number of preservatives present in food e.g Sulphite that is present in soft drinks also triggers the symptoms of food intolerance
  • Toxins: Food that is not properly stored increases the chances of bacterial contamination which become the cause of food poisoning5,6

Most common food intolerances


Lactose intolerance is the most common example of food intolerance, it is also referred to as lactose malabsorption. Many people have difficulty digesting lactose due to the absence of lactase enzymes after having dairy products, especially milk which causes stomach upset, diarrhea, and bloating.7


Casein intolerance is also caused due to intake of dairy products and milk, but it differs from lactose intolerance. Casein is a protein that has two beta types, which type A1 produces intolerance symptoms that are more similar to allergic reactions including runny nose, nasal congestion, fatigue, and digestive issues.8


Gluten intolerance develops after consuming food that includes wheat, barley, cereals, grains, and chocolates, also called non-celiac intolerance. Gluten is a mixture of proteins that causes inflammation and is unable to digest which produces bloating, constipation, fatigue, depression, and anxiety.9

Diagnosing an intolerance

Diagnosis of food intolerance is important to avoid the substance that triggers the symptoms and differentiate the type of intolerance, it can be more difficult if a person shows intolerance to more substances. Diagnosis should be done on the basis of the medical history of the patient which helps to indicate which food may produce that symptom. According to the history of the patient test serological and instrumental diagnostic test is recommended. Tests used for diagnosis are stool examination and endoscopy. The hydrogen breath test is used to determine lactose intolerance.10

Can you cure an intolerance?

Food intolerance can be avoided by the process of elimination diet. The role of diet is important in the cure of food intolerance. Food that contains a particular substance or chemical that triggers the response of food intolerance should be eliminated from the diet. Using an alternate source of that food like milk can be replaced by lactose-free, almond, and soya milk which are easily available in the market.

Supplements are required to fulfill the need for nutrients in the body. For symptomatic relief the counter medication is available.


Intake of food containing lactose, casein, gluten, and other food additives develops food intolerance in some people that cannot digest and produce food intolerance, which develops unpleasant symptoms. Food intolerance is not similar to food allergy but can be reversible, It is avoided by eliminating diet, removing all sources of that food from the diet or consuming a small portion of that food, and taking supplements that help in the digestion process.


  1. Lomer MCE. Review article: the aetiology, diagnosis, mechanisms and clinical evidence for food intolerance. Aliment Pharmacol Ther [Internet]. 2015 Feb [cited 2022 Aug 12];41(3):262–75. Available from:
  2. Ortolani C, Pastorello EA. Food allergies and food intolerances. Best Practice & Research Clinical Gastroenterology [Internet]. 2006 Jan 1 [cited 2022 Aug 12];20(3):467–83. Available from:
  3. Muthukumar J, Selvasekaran P, Lokanadham M, Chidambaram R. Food and food products associated with food allergy and food intolerance – An overview. Food Research International[Internet]. 2020 Dec 1 [cited 2022 Aug 12];138:109780. Available from:
  4. Farah DA, Calder I, Benson L, MacKenzie JF. Specific food intolerance: its place as a cause of gastrointestinal symptoms.Gut [Internet]. 1985 Feb 1 [cited 2022 Aug 12];26(2):164–8.Available from:
  5. Food intolerance and allergy—a review. QJM: An International Journal of Medicine [Internet]. 1983 [cited 2022 Aug 12]; Available from:
  6. Drisko J, Bischoff B, Hall M, McCallum R. Treating irritable bowel syndrome with a food elimination diet followed by food challenge and probiotics. Journal of the American College of Nutrition [Internet]. 2006 Dec [cited 2022 Aug 12];25(6):514–22. Available from:
  7. Catanzaro R, Sciuto M, Marotta F. Lactose intolerance: An update on its pathogenesis, diagnosis, and treatment. Nutrition Research [Internet]. 2021 May 1 [cited 2022 Aug 12];89:23–34. Available from:
  8. Pal S, Woodford K, Kukuljan S, Ho S. Milk intolerance, beta-casein and lactose. Nutrients [Internet]. 2015 Aug 31 [cited 2022 Aug 12];7(9):7285–97. Available from:
  9. И.А Б, В.И П, А.А З, Д.В Б. Безглютеновая диета в терапии внекишечных форм непереносимости глютена. 2020 [cited 2022 Aug 12]; Available from:
  10. Zopf Y, Hahn EG, Raithel M, Baenkler HW, Silbermann A. The differential diagnosis of food intolerance. Dtsch Arztebl Int [Internet]. 2009 May [cited 2022 Aug 12];106(21):359–70. Available from:
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Fatima Zehra

M. Phil in Pharmacy, Hamdard University, Pakistan

Fatima is a Pharmacist and Freelance Medical Writer with working experience in Pharmaceutical,
Hospital and Community Sector. She is passionate to educate people about health care. She has a
great interest to communicate complex scientific information to general audience using her
experience and writing skill.

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