Allergy versus Intolerance
- What's the difference?

Food allergies and food intolerances are very different. Despite this, it’s important to remember that whether your baby has a food allergy or food intolerance, it’s essential they get all the nutrients they need to grow and develop during this early and important part of life.


A food allergy

A food allergy happens when the body’s immune system reacts abnormally to specific foods. Allergic reactions vary in their severity, ranging from mild discomfort to serious reactions. During an allergic reaction to a food, the body’s immune system mistakenly recognises proteins in the food we eat as potentially harmful. As the body tries to neutralise the ‘harmful protein’ with substances such as histamine, which triggers an inflammatory response, allergic symptoms are experienced by the sensitised individual. Food allergies can be further classified as immunoglobulin E (IgE) mediated or non-immunoglobulin E (non-IgE) mediated reactions. IgE are antibodies produced by the immune system. IgE-mediated reactions are characterised by rapid appearance of symptoms, whereas non-IgE reactions are typically more delayed, occurring hours after exposure to the food allergen.1-2

A food intolerance

A food intolerance is an unpleasant reaction to food that, unlike a food allergy, does not involve the immune system but may occur due to incomplete digestion and / or absorption of a specific food.


Food allergy is thought to affect five to eight per cent of young children,3 with common childhood food allergies including milk, eggs and peanuts.2

Allergy symptoms4

IgE-mediated symptoms generally appear within minutes after a very small amount of food has been eaten. In comparison non-IgE mediated allergies are normally delayed reactions which appear hours or days after exposure to a food allergen. Common symptoms of allergy include:

(within two hours)
Non-IgE mediated (within
a few hours up to three days)
Digestive tract
  • Swelling of lips, mouth and tongue
  • Oral allergy syndrome
  • Vomiting
  • Colic
  • Diarrhoea
  • Reflux
  • Abdominal pain, bloating
  • Faltering growth
  • Allergic colitis (inflamed and damaged large intestine)
  • Diarrhoea
  • Constipation
  • Hives
  • Swelling
  • Redness of the skin
  • Severe itchiness
  • Anaphylaxis
  • Eczema
  • Hives (rarely)
Lungs and airways
  • Cough / wheeze / sneeze
  • Difficulty breathing
  • Anaphylaxis
  • Asthma
  • Abnormal heart rate
  • Low blood pressure


If you are concerned that your baby may have an allergy you should seek advice from your healthcare professional. They will be able to organise diagnostic tests based on your baby’s clinical history if appropriate.1

Your healthcare professional may ask you for your baby’s diet history and to keep a food diary to help them make a diagnosis.

Depending on the type of allergy your baby has, the following tests can be used:1

  • IgE-mediated
    Common tests for IgE-mediated allergies include a skin prick test and blood test. This is usually performed at an allergy clinic.
  • Non-IgE-mediated
    Diagnosis is normally made by dietary manipulation. This involves a trial elimination of the suspected allergen from the diet (usually for two to six weeks) followed by planned reintroduction of the suspected food allergen under the supervision of a healthcare professional.


Food allergies are normally managed by avoidance of the suspected allergen which could be causing the symptoms.2 You should always consult your healthcare professional if you are considering eliminating anything from your baby’s diet, they will be able to provide you with advice to ensure your baby receives adequate nutrition. The specific approach taken will depend on the age of your baby and whether you are breastfeeding or formula feeding.

Click here for a quick reference guide to the difference between food allergies and food intolerances.

If you have any concerns, please discuss these with your healthcare professional

Can you bust the food allergy myths? Why not test yourself here


  1. NICE, 2011: Accessed 14th August 2013.
  2. NHS Choices, 2012: Accessed 14th August 2013.
  3. NHS Choices, 2011: Accessed 14th August 2013.
  4. Shaw V and Lawson M (Eds). Clinical Paediatric Dietetics 3rd edition. Blackwell Publishing: Oxford 2010 pp260-261.

Back to top

RXANI140098 Date of preparation: March 2014