What is the difference between a food allergy and a food intolerance?

What is the difference between a food allergy and a food intolerance?

Food sensitivity is the umbrella terms for food allergy and food intolerances but they shouldn’t be confused with each other. Read on to find out what each of these mean and the differences between them.
Managing malnutrition after hip fracture Reading What is the difference between a food allergy and a food intolerance? 7 minutes Next How to make a Royal Coronation cake in 10 minutes!

This is a common question I am asked at my weaning workshops; how do I know my baby has an allergy to a food or an intolerance and what is the difference between the two?

Food sensitivity is the umbrella terms for food allergy and food intolerances but they shouldn’t be confused with each other. A food intolerance can be described as:

“Difficulty digesting certain foods and having an unpleasant reaction to them”. These symptoms can be delayed by up to 48 hours which makes them difficult to diagnoses, whereas a food allergy is described as “An immune response to food which can be life-threatening”.

A food allergy involves our immune system and involves the proteins found in foods and it are these proteins which trigger a response. This response can almost immediately after consuming a food or it could a delayed response, showing symptoms up to 48 hours after eating a food containing these proteins.

The most common type of allergic reaction is an Immunoglobulin E (IgE)-mediated food allergy. This in layman terms is when the immune system reacts to a normally harmless protein in food, due to the creation of IgE antibodies. This then results in chemicals being released which show themselves via physical symptoms in the body. Typically, these can be itching/swelling of the skin, running nose, coughing, vomiting and in more severe cases, breathing issues and anaphylaxis.

The top allergen foods are:

  • Cow’s milk
  • Hen’s eggs
  • Peanuts
  • Tree nuts (hazelnuts, almonds, walnuts, Brazil nuts, cashews and pistachios)
  • Wheat
  • Soya
  • Fish
  • Shellfish
  • Sesame

In the medical world, allergies were unheard of up until the 1900s, where a few cases of egg and Cow’s Milk Protein Allergy (CMPA) were documented and the first formal description of these allergies were only recorded in 1969. Allergies are on the rise globally however there is a lot of confusion between allergies and intolerances and unfortunately fake tests inflate these figures.

Many people will self-diagnose an allergy or a food intolerance from reading information online or from undertaking tests such as kinesiology or Vega testing and then start eliminating food from their diet, or the diet of their child with no need whatsoever and in some cases, causing more harm than good. The Vega test which is marketed as a tool to diagnose intolerances and allergies sounds scientific, until you realise it measures electrical resistance across the skin when you hold the suspect food in your hand – this is utter nonsense!

Another useless procedure is hair follicle testing for allergies and intolerances, this is completely ridiculous as hair is not involved at all in immune-based allergic reactions.

What is interesting to point out is that even with medical settings, the best food allergy tests that we have are IgE blood and skin prick tests – these are at best, 50% accurate. The blood test measures the levels of a protein that is often raised in some people with  allergies. The issue is that often they can be wrong and regularly it is shown different results in identical twins with the same allergy. Nearly half of people will test positive to at least one allergen, even if they don’t have allergic symptoms, and on the other hand, many children with symptoms may not have a positive test!

And so, you can see the issues! Best practice involves undertaking the IgE skin or blood test but alongside a full medical exam and history by a specialist who would then check the potential allergy with a food challenge (removing food from the diet and then slowly introducing it back).

If you suspect your family member has an allergy to a food, always speak to your GP and ask them to refer you to an allergy specialist or allergy team within your local hospital.

The symptoms associated with food intolerances can be similar to and mirror symptoms of Gastrointestinal disorders such as irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD) So when an intolerance is being diagnosed, it can be tricky and these other issues need to be ruled out first before diagnosis. It is also worth pointing out that most people can tolerate small amounts of the “intolerant” food. Most people will just need to re-assess the frequency of eating the problem food or the portion sizes.

Food intolerance does NOT involve the immune system and it is more associated with issues such as food being poorly digested. This can lead to symptoms such as excess wind, stomach cramps, sickness, diarrhoea or constipation. The most common food intolerances include:

Lactose (not to be confused with a milk allergy)

  • Lactose is the sugar food in milk and dairy products (cheese yogurt, butter etc). The body responds to the sugar rather than the milk protein which we see in a milk allergy. It is usually caused as the body doesn’t produce enough of an enzyme called lactase which we need to break down lactose in the body. Often, we see temporary lactose intolerance due to sicknesses such as gastroenteritis, food poisoning, antibiotics or chemotherapy. In many cases, the symptoms will improve over time.


  • This can be confusing as in addition to coeliacs disease (which is an autoimmune disease), we also have something called a gluten intolerance and is often described by health professionals as “non-coeliac gluten sensitivity (NCGS). It is however not clear how the immune system might be involved as no anti-bodies are produced and there doesn’t appear to be any damage to the gut lining.

Histamine intolerance

  • It is thought that only 1-3% of the population have a histamine intolerance. The body is unable to break down histamines in foods. Foods which contain high levels of histamines include cheese, certain meats, vegetables and fruits such as kiwi fruit, strawberries, aubergine, peppers and pineapple.


If you suspect a family member has an intolerance to a food, please avoid bogus intolerance tests and speak to a local registered Nutritionist or Dietician. To find one in your area, check out these trusted governing bodies – The Association for Nutrition or The British Dietetic Association

With Allergy Awareness Week taking place at the end of the month in the UK, it is really important to get a better understanding about the differences between having an allergy or having a intolerance to a food so we can make better choices for ourselves or people we care for.

If you are about to start weaning your baby who has an allergy, or you suspect your baby to have one, please contact Theresa via info@yourfamilynutritionist.co.uk and she can support you to introduce the allergenic foods safely and with confidence.

Leave a comment

All comments are moderated before being published.

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

Free shipping

Free shipping within the UK with orders over £25.