Food Allergy Versus Intolerance: What Is The Difference?

While the terms food allergy, intolerance and sensitivity are often used interchangeably, it is useful to understand the differences. Food sensitivities fall into two groups – primary and secondary. Primary means the reaction is directly caused by food, secondary means the reaction is directly caused by something other than food, such as gut disorders, drug treatments, long term high cortisol (stress) or low serotonin (mood). Primary Food Sensitivities then fall into two groups – non-immunological food intolerances include things like lactose intolerance which are genetic rather than immune related. Immunological food sensitivities are based on immune responses and split into two further subgroups – IgE – which is an immediate reaction or ‘food allergy’ and IgG – which are delayed reactions or ‘food intolerances’. When exploring food allergy vs intolerance, it helps to start with a broad definition of each condition.

By Nyanda Dennison, Clinical Nutritionist and Nutrition Coach

Food Allergy Definition

A food allergy is an immune system reaction that occurs soon after eating a certain food. Even a tiny amount of the allergy-causing food can trigger signs and symptoms such as digestive problems, hives, or swollen airways. In some cases, a food allergy can cause severe symptoms or even a life-threatening reaction known as anaphylaxis.

Immune System Involvement

When someone with a food allergy eats the allergen, their immune system mistakenly recognizes it as a threat and releases chemicals like histamines. This response can cause symptoms like itching, hives, swelling, shortness of breath, and, in severe cases, anaphylaxis. Common food allergens include peanuts, tree nuts, wheat, soy, fish, shellfish, eggs, and milk.

Food Intolerance Definition

A food intolerance can be either an immunological reaction or a non-immunological reaction. Food intolerances are delayed reactions, generally less serious than allergic reactions but no less problematic, symptoms include intestinal gas, abdominal pain, diarrhea, constipation, heartburn, reflux, bloating, brain fog and lethargy. 

Non-Immunological reactions

Non-immunological reactions cover all food reactions that are not driven by an immune response. For example, symptoms can be caused by a lack of certain enzymes needed to digest a food, as seen in lactose intolerance; when stress exacerbates digestive symptoms, or when reflux is triggered by spicy food or alcohol. 

Immunological reactions

Immunological food intolerances appear when the immune system reacts to food particles escaping through the intestinal lining, into the bloodstream, that are not fully digested. Symptoms of immunological food intolerance are generally less severe than allergic reactions and present as digestive issues, brain fog and lethargy. 

Types Of Food Allergy Immune Responses

IgG and IgE are immunoglobulins, which are a class of proteins that function as antibodies produced by the immune system in response to foreign bodies such as food antigens. 

• An IgG reaction can occur hours to days after exposure to an allergen, food or inhalant. This type of reaction is referred to as a delayed sensitivity reaction. 
• An IgE reaction occurs usually immediately after exposure to the allergen, food or inhalant.  This type of reaction is referred to as a Type I immediate hypersensitivity reaction or in some cases anaphylaxis. 

How Do Food Intolerances Develop?

In order to explain how food intolerances develop, it is important to understand how the gut functions.  Our bodies have several mechanisms to protect against toxins, such as physical barriers, digestive secretions, immune surveillance and enzyme systems that process toxins for excretion via sweat, breath, urine and faeces.  Approximately 70% of our immune system is located around the digestive system.

In a normal healthy person the small intestine behaves like a selective sieve, allowing only the broken down products of complete digestion into the bloodstream. These molecules are the amino acids, simple sugars, fatty acids, vitamins, and minerals that the body requires for all the processes of life to function properly. 

The small intestines allow only these smaller substances to enter the body because the cells that make up the intestinal wall are tightly packed together and located in between these cells are desmosomes. These adjacent cells stick together to form a strong, sturdy structure which prevents large molecules, microbes and toxins from passing through. 

The intestines also contain special proteins called ‘carrier proteins’ that are responsible for binding to certain nutrients and transporting them through the intestinal wall and into the bloodstream. In the intestinal tract, villi* serve as a point of absorption of these nutrients. Nutrients which have been broken down, such as glucose, amino acids or electrolytes are carried through the microvilli into the cells of the villus via active transport.  

In a healthy individual, food intolerances develop when the microvilli become damaged or inflamed, and the desmosomes weaken to allow larger molecules to pass through. This is called intestinal permeability.

*Villi are finger-like projections of the lining in the intestinal tract with hair-like cell membrane extensions called microvilli.

What Causes Intestinal Permeability?

• Stress    
• Low stomach acid and digestive enzymes     
• Poor diet (high processed foods and additives)    
• Alcohol      
• Parasites, yeast or bacterial overgrowth     
• Pharmaceutical drugs (especially anti-inflammatories, antacids, pain killers and anti-biotics)     
• Autoimmune conditions and inflammation associated with it

The above factors contribute to the intestinal lining becoming inflamed and the microvilli become damaged or altered. The damaged microvilli cannot produce the necessary enzymes and secretions that are essential for a healthy digestion and the absorption of nutrients ‐ so more inflammation occurs. 

When an area becomes inflamed this weakens the structure of the desmosomes and larger molecules of partially digested food proteins can escape through into the bloodstream. This activates the immune system to produce a protein called antibodies to locate and attack foreign objects and fight off these molecules – which may lead to IgG food intolerances. 

How To Test For Food Intolerance

The aim is to identify the root cause of your intolerance/s and design a custom treatment plan for you that incorporates diet modification and supplemental support to restore correct gut function.  

The most comprehensive way to identify food intolerances is to undergo Food Intolerance Testing.  There are a range of tests available, from 96 foods through to 208 foods, looking at IgA, IgE and IgG reactions. 

To help identify how these food intolerances developed we might also recommend doing additional gastro-intestinal tests. For example, if there is evidence of other factors affecting your intestinal integrity then we may recommend functional pathology testing to look for parasites, viruses, bacterial overgrowth, high stress, low serotonin, and digestive enzyme production. 

Food intolerance Treatment Options

Generally speaking, highly intolerant foods should be eliminated for three to six months depending on their severity in the test results.  Some foods may need to be eliminated longer term, and other foods may be consumed occasionally. 

This is also very dependent on what has led to development of these intolerances. For example, if the cause of your intestinal permeability is due to a parasite infection, it is important to get rid of the parasite, which may require additional treatment. 

If stress is an ongoing factor, this may need to be better managed, to prevent a ‘relapse of symptoms after the elimination period.

The team at Perpetual Wellbeing have vast clinical experience with interpreting test results and utilising various supplements to assist in restoring healthy gut function. 
Book in with one of our practitioners for a comprehensive consultation where the right tests can be selected based on your symptoms. You can also purchase a food intolerance test only, with a short interpretation session.