What is the Difference? Allergies Explained

Confused about Allergies?  You’re probably not alone..

There are various types of food reactions and there is equally much confusion about terminology used when it comes to diagnosis. Food allergies, sensitivities and Intolerance are sometimes used interchangeably, but the danger with this is we can undermine genuine life-threatening problems people experience when consuming provocative foods.

In my Book My Kids Can’t Eat That! I explain in detail the differences between these food reactions and more importantly what you can do about them.  Here is a brief summary of the most common terms used.


Food Reactions Are More Common Than You Think

Firstly, it’s worth mentioning that if you suffer with any type of food reaction you are not alone. The latest surveys estimate food allergies affect up to 8% of children and 3%-4% of adults. True food allergies also account for 29%-50% of all cases of anaphylaxis, which in turn cause 150-200 deaths annually (6-7 times more than deaths from insect stings. There are many more food allergies and food sensitivities around these days and of course many explanations as to the reasons why. This particularly seems to affect children too. From 1997 to 2007, the number of reported food allergy increased 18% in children.  Peanut allergy has tripled in children under the age of 18 years in a similar time frame, from 0.4% in 1997 to 1.4% in 2008.

These figures do not however include those with food sensitivities and intolerances – which is thought to affect many more children and adults and can often remain undiagnosed. On top of this are those diagnosed with coeliac disease, an autoimmune response triggered by eating gluten (found in wheat, barley and rye).


What is a Food Allergy?

In simple terms when we talk about a food allergy we are referring to an over-reaction of our immune system to a food that in non-allergic people would be seen as harmless. Our immune system is incredibly complex. It is designed to protect us from bacteria, viruses, parasites and anything else (e.g chemicals) that threaten our wellbeing. Normally it is efficient at telling the difference between its own cells and something foreign like a virus. Allergies arise when the immune system can’t recognise substances like foods as harmless and instead considers them something that needs to be attacked and destroyed. When this happens the body’s defences kick in which results in a wide range of symptoms we associate with allergies. How our immune system responds can vary which is why there are different types of food allergies.


IgE mediated Food Allergy

When doctors refer to allergies most of the time they are referring to IgE Food allergies (immunoglobulin IgE- immune response).  They may also be called ‘true’ or ‘classical’ food allergies. Here are some key features about these types of reactions.


  • This type of allergy is most common in children, rather than adults
  • Allergic symptoms tend to be immediate typically occurring within hours of eating and are normally very obvious.
  • IgE food allergies are often self-diagnosed as reactions are very obvious when you eat the food. Skin prick tests or blood tests are often used for confirmation.
  • Only a tiny amount of food is needed to trigger a reaction
  • They typically involve the production of IgE antibodies. These antibodies set off a series of reactions which produce vast quantities of inflammatory chemicals such as histamine.
  • The inflammatory chemicals produced result in a range of symptoms including itchy rashes, sneezing and in some cases anaphylactic shock.
  • Allergies usually run in families and there can be a genetic link. Children who are prone to IgE reactions are called atopic. If you have an IgE allergy you may also have related conditions such as eczema, asthma and rhinitis.
  • Virtually any food can cause an allergic reaction. The most common food allergens are cow’s milk, egg, peanut, soy, wheat, tree nuts, fish and shellfish.
  • If your child has been diagnosed with a food allergy, it may not be life-long. In fact, about 80% of children outgrow their milk and egg allergies. Peanut allergies are somewhat different: only 20% of peanut-allergic children eventually outgrow this allergy and are able to tolerate peanut in their diets.


What is a Non-IgE mediated food allergy?

This type of reaction does not appear to involve IgE antibodies and the reactions are somewhat complex. This type of reaction includes conditions such as eosinophilic gastroenteritis and atopic eczema. Reactions can be delayed – they may take 1-2 days to appear. Reactions appear to occur through the production of certain immune cells called T cells causing the production of various inflammatory chemicals which can affect any part of the body but particularly skin, respiratory system and digestive system

What is a Food Intolerance?

Food intolerances are more common than food allergies. The main difference between a food intolerance and food allergy is that a food intolerance does not involved the immune system.  Unlike some food allergies food intolerances aren’t life-threatening. However, they can cause a range of problematic symptoms.

According to the National Institute of Allergy and Infectious Diseases based in the USA, a food intolerance occurs when:


  • your body lacks a particular enzyme to digest nutrients
  • nutrients are too abundant to be digested completely, or
  • a particular nutrient cannot be digested properly.


Symptoms of food intolerances are exclusively gastrointestinal and mostly occur after sugar fermentation by the intestinal microbiota, leading to the production of gas, which causes bloating, abdominal pain, and irregular bowel movements. Common examples include lactose intolerance, or intolerance to excess fermentable oligo, disaccharides, monosaccharides and polyols (FODMAPs), sulphites, or histamine.

Food intolerances are not easy to diagnose. The easiest way to determine whether you suffer from an intolerance is to eliminate the offending foods from your diet and monitor symptoms to see if there are any improvements. Breath tests are available for lactose and fructose intolerance which can be undertaken if necessary.

Symptoms associated with food intolerances are generally influenced by the amount of the food or additive consumed. So unlike IgE food allergies this means you may not have to completely exclude all foods containing the offending ingredient. For example, some dairy products contain only traces of lactose which means they can be safely eaten.  In some cases, digestive enzyme supplements can be helpful to reduce symptoms.


What is a Food Sensitivity?

Food sensitivities are a bit more complex than food intolerances in that they may or may not involve the immune system. Food sensitivities can be harder to identify than true food allergies. Here are some key points to consider:


  • Reactions tend to be delayed – in some cases taking 1-2 days to appear. This can be make it hard to identify the culprit foods.
  • Symptoms are varied affecting many body systems (not just the digestive system) but are not normally life threatening
  • Other Immunoglobulins than just IgE may be involved.
  • Food sensitivities can be linked to other conditions such as eczema, asthma, arthritis, migraines, ear Infections, sinusitis and urticaria
  • Any food can cause such a reaction and the symptoms will vary from person to person.



The recommended approach to identify a food sensitivity is a challenge – elimination diet. Suspect foods are removed from the diet for 1-2 weeks to see if symptoms improve. Foods are then re-introduced one by one and symptoms monitored.  Food elimination and challenge diets are best undertaken under supervision of a qualified practitioner.

Non coeliac gluten sensitivity (NCGS) is an example of a food sensitivity. NCGS is characterized by symptoms that usually occur soon after gluten is eaten and will disappear with gluten withdrawal, within hours or a few days.  Well recognized NCGS symptoms include a combination of IBS-like symptoms: abdominal pain, bloating, changes in bowel movements (e.g diarrhea or constipation), and systemic effects such as “foggy mind,” headache, fatigue, joint and muscle pain, leg or arm numbness, dermatitis (eczema or skin rash), depression, and anemia.

Having a number of food sensitivities is often an indication that there are underlying digestive and immune imbalances that need to addressed. By avoiding the problematic foods temporarily while taking steps to rebalance the immune system and support the digestive system it may be possible to tolerate these foods in the long term.

One of the addition complications with these food reactions is that it is quite possible for them to coexist in the same person making differential diagnosis sometimes difficult.  There is also much concern regarding restricting your diet without a proper diagnosis. For example although FODMAPs can cause gut symptoms such as bloating, these foods actually inhibit, rather than cause, intestinal inflammation. This is partly because FODMAP foods induce beneficial changes to our gut flora and the production of short-chain fatty acids as well as other immune changes that benefit our health.  Therefore, excluding these from your diet long term does not make immunological sense and working with a suitably skilled practitioner to resolve your symptoms  should be a key objective of long-term resolution.

For more information about Food Reactions see my book My Kids Can’t Eat That: How to Deal with Allergies & Intolerances in Children.



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