This article was written by our regular contributor; registered dietitian – Maeve Hanan.
The terms food allergy and food intolerance are often used interchangeably in conversations, and while occasionally symptoms may overlap, they are two very different things.
This article will explain these main differences and summarise key facts related to food allergies and intolerances.
A food allergy occurs when the body’s immune system responds to a protein in a food, because it mistakenly thinks that this is a threat to the body.
Food allergies impact an estimated 1-2% of adults and 5-8% of children in the UK (1). The reason more children experience food allergies is that babies and young children often grow out of these.
The most common food allergies are a response to:
- Peanuts ?
- Tree nuts e.g. almonds, walnuts, Brazil nuts, pecans, pecan, cashew and pistachios ?
- Cow’s milk ?
- Soya ?
- Fish ?
- Shellfish ?
- Wheat ?
Based on the type of immune reaction that occurs, food allergies are classified as either IgE-mediated or non-IgE-mediated; or they may be a mixture of both (2).
Here are some differences between these types of allergy responses (2):
- IgE-mediated: IgE antibodies form in response to a specific protein, which causes an immune response involving the release of histamine from white blood cells. Symptoms usually appear within 2 hours and may include: swelling, rashes, hives, sneezing, congestion, coughing, wheezing, shortness of breath, gut symptoms, and in severe cases, anaphylaxis – which is a medical emergency.
- Non-IgE-mediated: This is thought to involve T-cells in the immune system and symptoms present more slowly than IgE-mediated reactions, often within 2 hours to 3 days. Symptoms include: eczema, rashes, constipation, diarrhoea, reflux, stomach pain and fatigue.
Food allergies need to be diagnosed and managed by a medical team. If you suspect you have a food allergy it is important that you strictly avoid the food trigger and speak to your GP. There are valid diagnostic tests to diagnose food allergies including IgE blood tests, skin prick test and food elimination.
In contrast to food allergies, food intolerances are a response to a food and don’t involve the immune system.
There are lots of different types of food intolerances and these are thought to be more common than food allergies. The symptoms of food intolerance can vary a lot depending on the type of food intolerance, but these can have a big impact on a person’s quality of life.
Common food intolerances include (2):
- Non-coeliac gluten sensitivity (NCGS): When coeliac disease and a wheat allergy have been ruled out but a person has symptoms in response to gluten, NCGS may be considered. Reported symptoms of NCGS include: diarrhoea, constipation, bloating, stomach pain, nausea, brain fog, fatigue, headaches, anxiety and depression. There is still controversy and disagreement about whether NCGS exists, and if so, whether it is caused by gluten or another protein in wheat.
- Lactose intolerance: Low levels of the enzyme lactase in the body leads to difficulty digesting lactose (a sugar found naturally in dairy). This can lead to gut symptoms such as diarrhoea, wind, bloating and stomach pain.
- Sensitivity to FODMAPs: FODMAPs are types of carbohydrates that are fermented by gut bacteria. Research indicates that those with IBS may be more sensitive to FODMAPS, so where appropriate a low FODMAP diet can be trialled with the support of a Dietitian in order to identify possible trigger foods. Check out this article for more information about the low FODMAP diet.
- Histamine intolerance: Histamine is a naturally-occurring chemical that our immune system releases as part of an inflammatory response. This is also found in certain foods and some people may be sensitive to this. Symptoms of histamine intolerance can include: rashes, hives, itching, swelling, flushing, headaches, diarrhea, anxiety, runny nose, congestion and breathing difficulties.
- Food additive or food chemical intolerance: These can vary a lot, but common symptoms include: headaches, hives, swelling, sinus issues, nausea, stomach pain and changes in bowel habits.
Food intolerances are a bit more tricky to diagnose and there are no reliable tests available – with the exception of lactose intolerance. The only way to diagnose other food intolerances is to exclude the suspected trigger food for a short period of time (usually 2-6 weeks) and then reintroduce suspected triggers one at a time and monitor any changes in symptoms during each stage. This should be done with the support of a Dietitian who has training and experience in this area in order to identify the possible triggers, avoid nutritional deficiencies and reduce unnecessary restriction in the longer term.
It is extremely important to see a doctor to rule out food allergies or other medical conditions before trailing an exclusion diet for a suspected food intolerance.
Be Aware of Woo Intolerance Testing
Reputable organisations including the UK National Institute of Clinical Excellence (NICE), the British Society for Allergy and Clinical Immunology (BSACI) and the British Dietetic Association (BDA) caution against the use of non-evidence-based allergy tests such as (2, 3, 4):
- Vega test
- Applied kinesiology
- Hair analysis
- Pulse testing
- The ATCAT (Antigen Leukocyte cellular antibody Test)
- Provocation – Neutralization testing
- Serum-specific IgG testing (A.K.A. the York test)
Many of these ‘tests’ are unfortunately widely available and can be presented in a way that seems medically legitimate. But as well as being unreliable and often expensive, these can lead to incorrect or missed diagnosis, unnecessary dietary restrictions and food anxiety.
Although both food allergies and intolerances can cause unpleasant reactions to certain foods, a food allergy involves the immune system whereas a food intolerance doesn’t. There is some overlap between symptoms that can occur in both cases, but an anaphylactic reaction only occurs in response to IgE-mediated food allergies.
If you are concerned that you or your child may have a food allergy or food intolerance it is really important to speak with your doctor about this. And please don’t waste your money, time and energy on any of the woo food intolerance tests listed above!
- FSA (2016) “Chief Scientific Adviser’s Science Report Issue five: Food allergy and intolerance” [accessed October 2021 via: https://www.food.gov.uk/sites/default/files/media/document/fifth-csa-report-allergy%20%281%29.pdf]
- NICE (2011) “Clinical guideline [CG116]: Food allergy in under 19s: assessment and diagnosis” [accessed October 2021 via: https://www.nice.org.uk/guidance/cg116]
- BSACI “Choosing Wisely on the use of alternative testing in the diagnosis of food allergy and Food intolerance” [accessed October 2021 via: https://www.bsaci.org/wp-content/uploads/2020/02/Choosing-wisely-ALTERNATIVE-TESTS.pdf]
- BDA (2021) “Food Allergy and Food Intolerance Testing: Food Fact Sheet” [accessed October 2021 via: https://www.bda.uk.com/resource/food-allergy-intolerance-testing.html]