Doctor's Review: Medicine on the Move

October 27, 2021

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Your food's bad chemistry

Though both cause reactions, food intolerance is different from food allergy. Unlike with food allergy, the symptoms of intolerance are caused by the inability of the body to break down or absorb certain components of a food. Intolerance is to a specific chemical, which can be found in many foods, and not just foods that are part of the same biological family. While lactose and fructose intolerance are diagnosed using hydrogen breath tests, other intolerances have to be diagnosed using a detailed medical history, along with a food and symptom journal. Here are some of the less well-known intolerances.1

Benzoate intolerance

Although naturally occurring in some foods, benzoates are most commonly found in processed food. Symptoms include asthma, hives, swelling, rhinitis, eczema, contact dermatitis, cutaneous vasculitis and headaches. Foods to avoid include many fruits and vegetables, spices, beverages and various processed foods.


Butylated Hydroxyanisole and Butylated Hydroxytolune are used in processed food to prevent rancidity. Symptoms include rashes and hives, and often affect people who are also sensitive to salicyate. These substances are found only in packaged foods, including margarine and oils, breakfast cereals and dried fruits.

Nitrate and nitrite sensitivity

Used to preserve food, especially meats, some also occurs naturally in food. At lower doses the symptoms include flushing of face, hives, headaches, and problems with digestion. Foods containing nitrates include vegetables like carrots, celery, potato, and spinach, as well as cooked meats, sausages, cold cuts and smoked fish.

Histamine sensitivity or intolerance

Occurring in about one percent of the population, it causes symptoms similar to an allergic reaction including anaphylaxis. Histamine is produced in our bodies. It is also produced by the bacteria in our guts, and the bacteria in/on food. It is also found in some manufactured foods and some fruits and vegetables, though we don’t know why it’s in the latter category. Food colourings and preservatives also release histamine into packaged foods.

Refer to a dietitian

Patients have many questions regarding foods to avoid, foods to include, how to cook and how to meet their nutrition needs. A dietitian can counsel the patient not only on what foods to avoid but more importantly what foods that they can eat, where to get it and how to make sure they are getting all the nutrients that they need.

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