What’s the Difference: Food Intolerance vs Food Allergy?


Most readers will have seen, or known about, a person who has experienced an adverse reaction to food at some point, but how do you know if it is a food intolerance? And, if it is, how can you make sure you can still get a varied diet? This brief article will provide a starting point on identifying the differences, spotting the symptoms, and what to do next.

First, you need to know the difference between a food allergy and a food intolerance.

  • Food Allergy:
    • “A food allergy is when the body’s immune system reacts unusually to specific foods. Although allergic reactions are often mild, they can be very serious.” (NHS, 2016).
    • This is a serious condition, which can be life-threatening, and affects up to 8% of children and 2% of adults in the UK (FSA, 2017).
    • The immune system (the body’s defence against infection) mistakenly treats proteins found in food as a threat and, consequently, a number of chemicals are released.
    • It is these chemicals that cause the symptoms of an allergic reaction.
    • The most common allergic reactions for children are: milk; eggs; peanuts; tree nuts (walnuts, Brazil nuts, almonds, and hazel nuts); fish; and shellfish (e.g. crab, lobster, and prawns).
    • The most common allergic reactions for adults are: peanuts; tree nuts; fruits (e.g. apples and peaches); fish; and shellfish.
    • Food allergies are divided into three types, depending on symptoms and when they occur: IgE-mediated food allergy; non-IgE-mediated food allergy; and mixed IgE and non-IgE-mediated food allergies.
    • Oral Allergy Syndrome: Some people experience itchiness in their mouth and throat, sometimes with mild swelling, immediately after eating fresh fruit or vegetables.
  • Food Intolerance:
    • This is any adverse reaction to food.
    • It is not life-threatening, because it does not involve the immune system.
    • People may suffer from symptoms such as diarrhoea, bloating and stomach cramps, however, no allergic reaction takes place.
    • Information on the number of people with at least one intolerance is scarce, partly because there are no reliable tests available, which makes diagnosis difficult.

What are the Main Differences between a Food Allergy and a Food Intolerance?

  • The symptoms of food intolerance usually occur several hours after eating the food;
  • A person needs to eat a larger amount of food to trigger an intolerance than an allergy; and
  • A food intolerance is never life threatening, unlike an allergy.

Differential Diagnosis (or What Else Could It Be?)

A lot of the symptoms, such as bloating and diarrhoea, overlap with other conditions, like irritable bowel syndrome (IBS). This makes it tricky to tell if it is a food or something else that is causing the problem. Conditions that can cause similar symptoms include:

  • IBS;
  • Stress and anxiety disorder;
  • Lactose intolerance;
  • Coeliac disease;
  • Inflammatory bowel disease; and/or
  • Food allergy.

Lactose Intolerance

Lactose is a sugar found in milk and dairy foods. A person with lactose intolerance does not make enough lactase, the enzyme needed to digest lactose. This then triggers symptoms like bloating, wind and diarrhoea. The amount of lactose that causes symptoms will vary, so find out how much – if any – you can comfortably manage. The major sources of lactose include cow, sheep and goat’s milk, soft cheeses, yogurt and ice cream.

Gluten Intolerance

Not to be mistaken for coeliac disease, which is a serious autoimmune condition that affects one in 100 people (my wife being one of them), gluten intolerance describes symptoms – such as tummy pain and diarrhoea – that arise after eating gluten, a protein found in rye, wheat and barley.

Gluten intolerance is also known as wheat intolerance, wheat sensitivity, and non-coeliac gluten sensitivity.

However, it is a controversial topic due to the limited evidence to suggest that it exists, and there are no tests to diagnose it.

It is also possible the symptoms may actually be down to difficult-to-digest sugars in wheat.

Things to avoid include bread, pasta, cereals, biscuits, cakes and pastries made from wheat, rye or barley. It is also important to note that some sauces may be thickened with flour that contains gluten. Some seasonings and spice mixes may also contain wheat, as well as malt vinegar. Not an exhaustive list, and it is best to read up on the rather large list of foods and food products that contain wheat/gluten.

What is the Difference between Wheat Allergy, Gluten Intolerance and Coeliac Disease?

  • Wheat allergy: Reactions usually begin within minutes, including itching, sneezing and wheezing.
  • Coeliac disease: This is a condition where the intestine lining cannot absorb and is damaged by gluten-containing foods including wheat, barley, oats and rye. Coeliac disease is neither an intolerance nor an allergy.
  • Gluten intolerance: Symptoms like bloating, cramps, diarrhoea and sickness come on quite slowly, usually hours after eating wheat. There is no diagnostic test.

Other Food Intolerances

While the two most common intolerances are lactose and gluten, there are others, including:

  • Fructose:
    • This is a sugar found in many fruits and vegetables, as well as honey and some sweeteners.
    • High intakes can be hard for some children to break down, resulting in tummy pain, wind, and diarrhoea.
    • Keep things varied by serving lower fructose fruits and vegetables such as kiwis, bananas, berries, peas, spinach, sweet potatoes, sweetcorn, carrots, and courgettes.
  • Egg:
    • This is when the body cannot digest or has an adverse reaction to certain parts of an egg.
    • A child with an egg intolerance may find that, in time, they ‘grow out of it’ – usually by the time they start school.
    • Some foods that contain eggs may surprise the reader: fizzy drinks are sometimes made with eggs; and they are also a key ingredient in ice cream and marshmallows.
  • Soya:
    • This is a legume found in many manufactured goods, including cake, bread, biscuits, crisps, and sauces.
    • Symptoms of a soya allergy/intolerance include: skin rashes like eczema or hives; abdominal pain; nausea; and diarrhoea.
    • It can be difficult to avoid soya, but many fresh foods that have not been processed or had additional ingredients or seasonings added during cooking are soya free.
    • You may be able to find soya free products in the supermarket aisle, usually by the Free From section.

Shopping Made Easier

A number of supermarkets have introduced ‘custom filters’ that enable online shoppers with multiple dietary needs to only find products that match their diet. It is a useful search tool that can aid online shoppers with complex dietary needs to find the food that best suits their needs.

Allergen Information

The way allergens are labelled on pre-packed foods changed with the introduction of legislation which came into force in December 2014. This introduced a requirement that food businesses must provide information about the allergenic ingredients used in any food they sell or provide. The relevant legislation includes:

Food businesses – which includes restaurants, cafés and takeaways, and businesses that produce, manufacture or pre-pack food – must declare if the food contains any one of 14 major allergens as ingredients (either on a menu or label), and include:

  1. Celery.
  2. Cereals that contain gluten: including wheat, rye, barley and oats.
  3. Crustaceans: such as prawns, crabs and lobsters.
  4. Eggs.
  5. Fish.
  6. Lupin.
  7. Milk.
  8. Molluscs: such as mussels and oysters.
  9. Mustard.
  10. Tree nuts: including almonds, hazelnuts, walnuts, Brazil nuts, cashews, pecans, pistachios and macadamia nuts.
  11. Peanuts.
  12. Sesame seeds.
  13. Soybeans.
  14. Sulphur dioxide and sulphites (if they are at a concentration of more than ten parts per million).

The Food Allergy and Intolerance Research Programme, of the UK’s Food Standards Agency, identifies risk factors associated with food allergies, and provides advice to consumers and food businesses.

‘May Contain’

When buying foods, you may notice on the label that there is a notice stating a ‘May Contain’ warning that there could be small amounts of an allergen in a food product, although it is not a legal requirement to label food in this way.

Other terms for May Contain include ‘Made on equipment that also processes’ and ‘Made in a factory that also handles’. These terms only state what the risk could be caused by but not how serious the risk is.

Strike a Balance in Your Diet

  • Lactose:
    • Removing milk and dairy can mean missing out on calcium, protein and B vitamins, so you will need to ensure you get these elsewhere.
    • Try to go for brands with added calcium. Lactose-free milk and yogurt are ideal swaps as they have had the lactose removed, but are nutritionally similar.
    • Other options include unsweetened dairy alternatives made from soya, oats, almonds or coconuts – suitable for kids from the age of one as part of a healthy balanced diet.
    • Rice milk is not recommended for children under five.
  • Gluten:
    • You do not necessarily have to miss out on your favourite meals.
    • A number of supermarkets, restaurants, and food manufacturers offer or produce gluten free products – although the range can be small.
    • Try to use naturally gluten-free grains such as quinoa, buckwheat, polenta, potatoes, and rice. However, be aware that the taste and consistency may be different to what you are used to – play with the recipe until you achieve the desired result.

If you suspect a food allergy or food intolerance, then consult with a healthcare professional, such as a GP or dietitian, before making any radical changes to your diet. A lactose-free, gluten or wheat-free (or any other free from) diet should only be adopted under the direction of a dietitian or doctor, especially when involving children.

Are You Affected?

Think you, a family member or friend might have a food intolerance? Follow these step-by-step tips:

  • Speak to your GP: They will take a full history of your health and may then refer you to a specialist dietitian.
  • Keep a food and symptoms diary: Record what you eat and any responses, including how long after eating the reaction comes on.
  • Cut out suspected foods: The way a dietitian will diagnose a food intolerance involves cutting out the suspected problem food from your diet to see if symptoms improve (known as a trial elimination diet).
  • Add them back in: The dietitian will then reintroduce the suspected problem food to see if symptoms return. Removing foods in this way should only be done under the supervision of a healthcare professional (e.g. GP or registered dietitian).
  • Food allergy test/panel: A food allergy test can determine whether or not you are allergic to various foods.

Useful Links


FSA (Food Standards Agency) (2017) Allergy and Intolerance. Available from World Wide Web: https://www.food.gov.uk/safety-hygiene/allergy-and-intolerance. [Accessed: 21 August, 2018].

NHS (2016) Overview: Food Allergy. Available from World Wide Web: https://www.nhs.uk/conditions/food-allergy/. [Accessed: 21 August, 2018].


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