Food Allergy, Intolerance or Sensitivity? It matters....

July 12, 2015


The terms food allergies, food intolerance and food sensitivity are thrown around synonymously in dietary discussions these days, without much understanding of what they actually mean and the differences between them. Understanding these differences can play a critical part in the success of elimination diets for your health concerns.

A food intolerance, is when the digestive system is unable to digest a food properly, which can then lead to symptoms relating to this maldigestion issue. Lactose intolerance is the most common example. When someone is lactose intolerant, they lack enough of the enzyme lactase which is responsible for breaking down lactose (milk sugar) for absorption in the small intestine. Normally all sugars are digested and absorbed in the small intestine. In this example, the sugar molecule (lactose) passes through the small intestine into the large intestine undigested and in "full sugar" molecular form. The large intestine is filled with yeast and bacteria (microflora). What happens to sugar (lactose) when it gets exposed to yeast in a warm moist environment?  Almost instant fermentation which creates a gas and fluid production in the large intestine. This will ultimately lead to cramping, pain, gas, bloating and loose bowel movements. These are the common symptoms of a lactose intolerant reaction.

The key point to understand here is that the symptoms of the intolerance (gas, bloating, loose bowels) were caused by a food product (lactose) getting somewhere where it wasn't supposed to be undigested (large bowel) and it reacted with the microflora in the bowel and caused symptoms. At no point did the Immune system ever attack the lactose.

A food allergy, implies the immune system is reacting to and attacking the foods and causing symptoms through this immunological attack. This is a critical point to understand in order to begin to decipher your true food reactions. A food allergy can affect the digestive tract but it can also affect you anywhere in your body where the immune system is present.

The main differences between Food allergy reactions and Food intolerant reactions are outlined in the chart below.

    Food Intolerance's

  •     Cause symptoms by improper digestion of a food

  •     Symptoms are usually localized to the digestive tract

  •     Symptoms often occur shortly after eating the intolerant food (Minutes to hours)

  •     Symptoms usually resolve after passing of the intolerant food


    Food Allergies / Sensitivities

  •     Cause symptoms by an immune/inflammatory reaction to a food

  •     Symptoms can occur in the digestive tract or anywhere else in the body

  •     Symptoms can occur shortly after eating the food, or can be delayed by up to several days

  •     Symptoms can persist for several days to weeks off one food reaction

If you have inflammatory issues anywhere in the body, it's critical that you understand the differences between  food allergies and food intolerances. And it's also critical that you understand that if you have food related inflammatory issues in the body, they have to be associated with food allergies (immune related) rather than food intolerances. The immune system is what creates inflammation in this regard, food intolerances do not.

Two distinct types of Food Allergies

Most people are aware of anaphylactic types of food allergies. A child with a peanut allergy is the classic example. These types of allergies are called type I hypersensitivity reactions. The keys to understanding this type of allergy is that they are mediated by a specific type of immunoglobulin (natural antibody) called IgE. These antibodies cause an immediate release of histamine in the affected tissue, and histamine causes an immediate inflammatory reaction in the tissue (swelling, redness, itchiness, welts, etc.)  Symptoms of a type I allergic reaction always happen immediately after you eat the offending food. There is an obvious cause and effect with this type of reaction. When a child eats a peanut, their throat swells up immediately and they need an epi shot immediately to survive. It's very obvious the peanut caused the reaction.

There are three other types of hypersensitivity (allergic)  reactions called types II, III and IV hypersensitivity reactions. These reactions involve completely different types of immunoglobulins called IgG and IgA. The key difference between these immunoglobulins and the type I IgE immunoglobulins, is that these antibodies cause delayed reactions in the body, sometimes delayed by up to a week to ten days. If you eat a peanut and have a type I reaction, your throat will swell up immediately and you will know immediately that you shouldn't eat peanuts again. If you eat a food and have a delayed type II, III,  or IV reaction, you might not have a symptom relating to that food for several days to a week later. It's unlikely that you'll be able to associate a symptom one day, with a food you ate a week earlier. This is why people often never figure out their food related issues and never associate their symptoms with their diets.

The IgA and IgG components of the immune system are the same parts of the immune system that react against a vaccine. When someone receives a vaccination to travel overseas, they have to get the shot 1-2 weeks prior to travel in order for the immune system to have time to react to the vaccine and produce the antibodies to it. When these antibodies are produced against a food, the reaction is the same and it can take several days for the antibodies to be produced, travel back into the blood stream get out of the blood stream and into the tissue to cause the reaction.

Also important to understand, is how much food in takes to create a systemic IgA or IgG antibody reaction. When they give you a tetanus shot, they give you a 1/2 ml dose of the vaccine, and this will produce enough antibodies to go through the entire system and stay in your system for ten years. Your immune system only needs a micro dose of the offending food, to create a million fold antibody response against, that can stay in your system for weeks to months.

You can eat a food today, have a symptom caused by that food a week from today, and that symptom can linger on for several weeks... all after eating that one food item, one day. This delayed type of food reaction is extremely difficult for the patient to understand and makes it nearly impossible to try and figure out the association between their diets and symptoms associated with them.

Delayed onset allergic food reactions can also lead to food intolerances. Imagine eating a food today that you have a delayed response to. This reaction could come back and inflame the digestive tract a week later. This inflammation can affect proper enzyme production in the intestine, which can then lead to intolerances to the foods those enzymes are meant to digestive. You eat one food type today, it affects you digestive tracts ability to digest another type of food a week later. This becomes very confusing for the patient to figure out. Many times if you address the underlying delayed type food allergy, you can improve other food intolerances that you may be aware of.


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Dr. Scott Woodworth
Naturopathic Doctor

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