Allergies and intolerances - understanding the difference

Allergies and intolerances - understanding the difference

It is estimated between 5-10% of children have an allergy in the UK.

If you’re a parent within this group, you will know the impact this can have on your day to day life as a family and all the considerations that are needed to protect your child.

However, the words allergy and intolerance are often thrown around, and there is confusion over their meanings. If you suspect your child might indeed have an allergy or intolerance to a food, what is the right thing to do next?

Let’s explore and firstly get clear on some definitions.

Food Allergies

This involves the immune system in some way, as it reacts to a protein found in food, mistaking it for something that is a threat to the body. Symptoms can range from immediate life- threatening ones, such as anaphylaxis, or may appear over a period of time, depending on which parts of the immune system are involved. Allergies can therefore be described as either IgE or none IgE mediated.

IgE mediated allergies

IgE mediated allergies are associated with symptoms such as a rash, swelling, breathing difficulties, nausea and vomiting and any of these can occur quite quickly after the offending food has been eaten e.g. peanuts.

When the body reacts to a food protein, the immune system creates antibodies, as a way of remembering this food, the next time it ‘strikes’! These are known as IgE antibodies, hence the name. So, when the food is eaten again, the body is armed to release substances that remove it, setting off a cascade of unpleasant symptoms. These IgE antibodies are found skin, lungs and mucous membranes, so a child may experience swelling, itchiness and breathlessness, for example.  

None IgE mediated allergies aren’t as well understood, but we know the immune system is still involved in some way. Symptoms tend to take longer to appear – hours or days later - and usually involve the gut, for example diarrhoea and vomiting.

Below are the common allergens which, by law, have to be declared and written in bold on food labelling.

  • Cereals containing gluten, including wheat, rye, barley and oats
  • Shellfish and lupin molluscs, including prawns, crab, lobster and crayfish
  • Eggs
  • Fish
  • Peanuts
  • Soya beans
  • Milk
  • Nuts
  • Celery
  • Mustard
  • Sesame

If you suspect your child has an allergic response to a food, it’s really important you see your GP.

To diagnose an allergy

There are IgE antibody tests and skin prick tests. Depending on the symptom history and overall picture your GP might refer your child to a specialist team and/or order some of these tests themselves. It’s important to consider the full picture and interpret the tests in context of this too as it’s complex stuff and even the most gold standard of tests can sometimes reveal a false positive.

Food Intolerances

Now let’s talk about food intolerances, because this is where it can get a bit murkier.

These are a lot more common and do not involve the immune system. Instead the digestive system is letting us know that a particular food is irritating it, or it is unable to digest it.

Symptoms might include diarrhoea, bloating, fatigue or constipation. These symptoms are not immediate and may build up over a period of time. It will also depend on how much of the food is eaten, as a certain amount might not cause any problems at all.

This makes diagnosis difficult, as there are also multiple confounding factors that can influence our gut health and digestive responses, for example, bacterial or viral infections or stress and anxiety.

Common foods or components that are associated with intolerances include:

  • Gluten
  • Histamine
  • Wheat
  • Lactose
  • Salicylates
  • Sulphur Dioxide

It’s understandable our children’s needs are front of mind, but it’s important not to get lost in a plethora of tests on the internet or high street, that promise solutions, without having some credible science to support them. These tests can cause mis or delayed diagnoses and increase the risk of nutritional deficiency in children.

Alternative testing

IgG analysis

IgG antibodies are not regarded by immunologists as a reliable diagnostic tool for food allergy. IgG antibodies will be present if a particular food has been eaten, not necessarily because the food has caused a problem.


This looks at energy fields and changes can be detected through muscle weakness which is said to indicate an intolerance.  We have no scientific evidence that this practice works.

Hair analysis

Supposedly testing hair for minerals can indicate food intolerances. These tests have been shown to be highly variable and unable to conclude anything in particular.

Electrodermal (Vega) test

This looks at energy levels on exposure to a potential allergen. There is no scientific grounding to support this.

To diagnose a Food Intolerance: Food Exclusion and Reintroduction

The only reliable method of detecting a food intolerance is takng the suspected food out of the diet, and then reintroducing it some weeks later to see the affestcs.

Nutritional considerations

However, removing lots of foods from the diet to work out what’s causing the problem can lead to missing nutrients needed for growth and development. Foods marketed as suitable alternatives might not provide all the same nutrients. For example, within the dairy free, plant-based milk market, there are huge variations in protein and mineral contents of the milks, with some not recommended for children until they reach a certain age.

Sources of help

The role of a Registered Dietitian would be to assess your child’s needs and provide you with tailored advice. You should ask your GP to refer you, if you are unsure or seek someone who works privately.

If you’re thinking your child has an allergy or intolerance, a good place to start aside from a visit to your GP, would be for evidence based, free information.

Laura Clark
Written by: 
Laura Clark