Food Intolerance: Causes And Symptoms

how do food intolerances develop

The food intolerance is also known as non – IgE mediated food hypersensitivity or non – allergic food hypersensitivity. It refers to difficulty in digesting certain foods. It is important to know that the food intolerance is not same as food allergy. Food allergies are triggering the immune system, while the food intolerance does not do it. Some people can suffer from digestive problems after eating certain foods, even though their immune system has not reacted, there is no histamine response. Foods which are most commonly associated with the food intolerance include grains that contain gluten, dairy products and foods that cause intestinal gas buildup, such as cabbage and beans. [1]

causes of food intolerance

Food intolerance symptoms

In many cases, it is difficult to determine if the patient has food intolerance or an allergy, because the signs and symptoms often overlap. When someone has food allergy, even the smallest amount will result in symptoms, as may be the case with peanuts. While, with the food intolerance, tiny amounts will usually have no effects. Generally, the symptoms of food intolerance take longer to emerge, compared to food allergies. Typically, onset happens several hours after ingesting the offending food or compound and it can persist for several hours or days.

In some cases, the symptoms of food intolerance can take 48 hours to arrive. Some people can be intolerant to several groups of foods. This makes harder for doctors to determine whether it might be a chronic illness or food intolerance. It can take a long time to identify which foods are culprits. The most common symptoms of food intolerance include [1]:

  • Hives
  • Bloating
  • Irritable bowel
  • Migraines’
  • Stomach ache
  • Headaches
  • Feeling under the weather
  • Runny nose
  • Cough

Food intolerance causes

There can be different causes for food intolerance, such as

  • Salicylates: They are present in many foods. The salicylate intolerance is also known as salicylate sensitivity. It happens when somebody reacts to normal amounts of ingested salicylate. Salicylates are derivatives of salicylic acid that it happens naturally in plants as a defense mechanism against harmful fungi, bacteria, diseases and insects. These chemicals are found in many foods and many people who consume foods with salicylate do not have any side effects. But, some people can notice some symptoms after eating large amounts. People, who are salicylate intolerant, should avoid foods which have high levels of these components. Salicylates are present in most plant – sourced foods, such as flavor additives, tea, herbs, spices and majority of fruits and vegetables. Citrus fruits, berries, tomato sauce and mint – flavoring are particularly high in salicylates. Also, processed foods with flavor additives have high amounts of salicylates. [2,3]
  • Histamine: Histamine can naturally happen in some foods. Some foods, like fish which has not been properly stored, can have an accumulation of histamine as they rot. There are many people who are particularly sensitive to this naturally – happening histamine and they develop skin rashes, nausea, vomiting, diarrhea and abdominal cramps. Often, these symptoms are similar to the anaphylaxis, which is a strong allergic reaction. [4]
  • Food poisoning – toxins: Some foods have naturally – occurring chemicals which can have toxic effect on people and they can cause vomiting, nausea and diarrhea. Undercooked beans have aflatoxins. They can cause extremely unpleasant digestive problems. But, fully cooked beans do not have toxins. This is a reason why some people wonder why they react to beans after one meal and they do not react after another meal. [5]
  • Chemical causes of food intolerance: There are some chemicals in foods and drinks which can cause intolerance, including amines in some cheeses, and caffeine in chocolates, tea and coffee. Some people can be more susceptible to these chemicals than others. [6]
  • Absence of an enzyme: Enzymes are needed to digest the food fully and if some of the enzymes are missing, then the proper digestion can be undermined. People, who are lactose intolerant, do not have enough lactase, which is an enzyme that breaks down the lactose into smaller molecules that the body can break down further and absorb through intestine. If the lactose remains in the digestive tract, then it can cause gas, diarrhea, bloating, stomachache and spasm. [7]


[1] Harvard Women’s Health Watch. Food allergies and food intolerances. Harvard Health Publishing. 2011. Retrieved from

[2] Baenkler HW. Salicylate intolerance: Pathophysiology, clinical spectrum, diagnosis and treatment. Deutsches Arzteblatt international. 2008;105(8):137–42. doi:10.3238/arztebl.2008.0137

[3] Zopf Y, Hahn EG, Raithel M, et al. The differential diagnosis of food intolerance. Deutsches Arzteblatt International. 2009;106(21):359–70. doi:10.3238/arztebl.2009.0359

[4] Comas-Basté O, Sánchez-Pérez S, Veciana-Nogués MT, et al. Histamine intolerance: The current state of the art. Biomolecules. 2020;10(8):1181. doi:10.3390/biom10081181

[5] Granum PE, Lund T. Bacillus cereus and its food poisoning toxins. FEMS Microbiology Letters. 1997;157(2):223-8.

[6] Temple JL, Bernard C, Lipshultz SE, et al. The safety of ingested caffeine: A comprehensive review. Frontiers in Psychiatry. 2017;8:80. doi:10.3389/fpsyt.2017.00080

[7] Szilagyi A, Ishayek N. Lactose intolerance, dairy avoidance, and treatment options. Nutrients. 2018;10(12):1994. doi:10.3390/nu10121994


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