Context: Food Allergy and Reactions

Food Allergy, Intolerance, Sensitivity, Reactions

This is a confusing topic, because many different types of problems can give rise to health problems that can be described as adverse reactions to food.

The hall-mark of an immune response is that it can be triggered by very small, and even very tiny, “doses” of exposure to foods. When the reaction is milder or moderate, a stronger response with a larger exposure is the common experience. For anaphylactic type of reactions, when the sensitivity has become more severe, even a trace of exposure can lead to very rapid severe reaction and death. A big problem is that the person may start to take it for granted that they will have milder or moderate reactions, yet on the next exposure have a severe reaction without any warning.

In Canada, there has been a tremendous increase in the number of people seen in the emergency department for anaphylactic reactions to foods. Deaths due to food anaphylactic reactions are particularly tragic because they are avoidable and because they often involve young people.

Immune System Responses:

  • anaphylactic reactions are an immune system response that, when severe,  can cause death very quickly. Anaphylaxis involves the IgE part of the immune system. Milder anaphylactic reactions may not be recognized for what they are and may be falsely dismissed as unimportant.
  • an auto-immune attack on one’s one body tissues can be provoked by exposure to a food component – the only example known to occur is celiac disease.
  • it is now thought, but far from proven, that the syndrome we call “non-celiac gluten sensitivity” (NCGS) is caused by a non-IgE immune system response to one or more of the types of molecules in gluten-containing grains.
  • for decades there has been a running controversy about the existence or not of other types of immune-based adverse reactions to foods. The common term used is “food sensitivity”.
  • there is a syndrome called “oral food allergy” which most people and most health care practitioners have never heard of, but I find is not rare.
  • there can be contact allergy from food touching the skin.
  • there can be an allergic response to inhaling food – for example “baker’s asthma” from inhaling wheat flour. (Similarly asthma can occur from other exposures such as wood dust from specific species.)
  • reactions to histamine present in foods are not caused by an immune reaction, but look like allergic reactions because histamine is one of the body chemicals released during an immune reaction and which cause many of the symptoms of an allergic reaction (why anti-histamine medications are used for allergy).

Food Intolerance Not Based in the Immune System

For more on various gut and other symptoms related to foods and diet, have a look at other pages on this site, such as under the “Gut” heading.

  • there are various ways that foods can provoke digestive symptoms that may seem like food allergy such as –
    • poor digestion of one or more of various sugars or other carbohydrate molecules naturally present in foods. Although these are all normal components of foods, there is a lot of variability between different people in how much of one or another of these challenging molecules their digestive system can handle well. The collective term for these difficult-to-digest sugars or complex carbohydrate molecules is “FODMAPS”. This term includes some things you might not be familiar with, but also common problems such as
      • lactose intolerance,
      • fructose intolerance
      • gassiness with eating beans
    • fatty foods can cause symptoms by various means, including –
      • if the gallbladder has stones, there may be pain when fatty meals stimulate the gallbladder to do it’s normal thing of contracting to deliver bile fluid to the digestive tract
      • there is a condition referred to as BAM – bile acid malabsorption
      • slowing the movement of food out of the stomach after meals, thus making reflux more likely, particularly when going to bed within a few hours after a large meal.
  • some people have an intolerance to handling certain specific molecules in food, such as
    • oxalate
    • purines, which are metabolized to uric acid