Food allergy and food intolerance
According to the NHS, nearly two people out of every 100 in the UK have a food allergy and around one in five adults report having a food intolerance.
There are now many different names used to describe the body’s adverse reaction to certain types of food, including food intolerance, food allergy and hypersensitivity. These names can often lead to confusion and misunderstanding of what a food allergy or food intolerance is. This confusion can then cause people to seek information and advice from unreliable sources.
On this page
Allergy or intolerance?
A food allergy is a reaction caused by the immune system. Symptoms can range from mild to severe and may affect the gut, the skin, breathing ability or the body’s circulation system.
A food intolerance is more common, though can be difficult to diagnose. Food intolerances are not caused by an immune system reaction. Instead, they are caused by a number of factors, resulting in unpleasant symptoms which may last for several hours or even days.
How can a nutrition professional help?
If you suspect you or someone you know may have a food allergy, a food intolerance, coeliac disease or gluten sensitivity, then it is important to seek professional diagnosis from your doctor.
A qualified nutrition professional can help you understand the foods that are causing your symptoms and assist you in the successful implementation of an exclusion and reintroduction diet. They will advise you on how to avoid the confirmed/suspected allergen, to prevent symptoms while maintaining a healthy, balanced diet that meets your nutritional requirements.
You can find a nutrition professional you resonate with using our advanced search tool. If you are not ready to contact a professional just yet, you can learn more by browsing our Nutrition Topics pages.
Following any form of exclusion/elimination diet can be very dangerous if not done under the close supervision of a qualified nutrition professional. The reason for this is due to the risk of missing out on vital nutrients, especially when major food groups are excluded. For example, excluding wheat and dairy needlessly can lead to nutrient deficiencies and diseases long term.
What can I expect when visiting a nutrition professional?
You may be asked to complete a food and symptom diary prior to your first appointment. This will give the dietitian/nutritionist a better picture of what you eat and which foods are likely to be causing symptoms.
During your first appointment, the nutrition professional will gather as much information as possible about you. This may include questions about your medical history and more detailed questions about your diet. From this, a personalised meal plan/diet with supporting written information will be provided for you.
For people with undiagnosed food intolerances, it is recommended that you return for a follow-up appointment four to six weeks after the first appointment. You can review your progress and make necessary adjustments to your diet, depending on whether your symptoms have resolved or not.
For people with a diagnosed food allergy, it may be that you only require one or two follow-up appointments to ensure that the correct foods are being avoided and that the diet is well balanced. Further face-to-face appointments or contact via email can usually be arranged as required.
A food allergy is when the immune system reacts to certain foods. While they are often mild, they can be more severe and in some cases, life threatening. If the immune system mistakenly treats the food as a threat, it will release a number of chemicals.
When the chemicals are released, the symptoms develop. Symptoms of a food allergy include an itchy throat, mouth or ears, a rash (or hives), vomiting and swelling of the face, lips or tongue.
Almost any food can cause a reaction and people will respond differently to different foods. Yet there are certain foods recognised for commonly causing allergies, especially in children. Common allergens include milk, eggs, peanuts, fish and shellfish.
IgE food allergy and Non-IgE food allergy
Allergic reactions are made up of two key responses within the immune system. The first is the production of an antibody known as immunoglobulin E (IgE) which circulates within the blood stream. The second response is the mast cell, a cell which occurs in body tissue but is common in sites of allergic reactions.
Children are more likely to suffer an allergic reaction than adults, especially those under three years old. This is often caused by another type of food allergy, known as a Non-IgE food allergy. This form is also caused by the immune system, but not through an antibody reaction.
Anaphylaxis or anaphylactic shock is a severe and potentially life-threatening allergic reaction. It can affect many areas of the body. A sufferer may experience breathing difficulties, dizziness and severe swelling to the lips, throat and hands.
Individuals who have a history of anaphylaxis may carry an auto-injector of adrenaline, the anti-allergy medicine used to treat the reaction. This should be injected into the outer-thigh muscle and held in place for five to 10 seconds.
Even if the individual experiencing a reaction carries an auto-injector, they should always be considered a medical emergency. If you suspect you or someone else is having a reaction, then it is important you call an ambulance as quickly as possible. While this can be life-threatening, if treated quickly and effectively, most individuals will make a full recovery and not experience any long-term complications or side effects.
One of the most effective ways to manage a food allergy/food intolerance is to identify and then avoid the food that contains the suspected food allergen/trigger/gluten. This can be difficult, as some ingredients (i.e. wheat, nuts and milk) are found in many recipes and shop-bought products. One way to manage what you are eating is to read food labels.
In December 2014, the allergen labelling law changed so as to make it easier for those living with a food allergy or intolerance to buy food. The law states that all allergens have to be in bold or highlighted and appear on one place (ingredients list) on all pre-packaged products. For foods sold without packaging such as in a bakery, cafe or pub, allergen information will have to be provided either in writing or verbally.
If you are still unsure, you may benefit from contacting a nutrition professional for support and advice. Before making any drastic changes to your diet, it is important to talk to a medical professional.
If you suspect you are suffering from an allergic reaction, you should visit your GP immediately. They will take a full and detailed medical history and if possible, arrange the appropriate tests. Once the allergens have been identified, your GP will then be able to recommend treatment. If they are unable to carry out allergy testing, they may refer you to an allergy clinic for further assessment.
There are a number of allergy tests that you may take, depending on your reaction and type of allergy. If you develop symptoms quickly (an IgE food allergy) you may be given a blood test or a skin-prick test. If your symptoms develop over hours or days (non-IgE) you will typically be advised to go on a food elimination diet.
This is a common form of food allergy test. The procedure involves a small needle or lancet which is used to pierce the skin. This allows a small dose of the known-allergen to come into contact with your immune system. In some cases, the practitioner will perform the test using a sample of the suspected food.
Usually, itching, swelling or redness of the skin will indicate a positive reaction. The reaction will typically develop within 20 minutes and should fade within an hour.
A blood test involves a blood sample being taken and sent for assessment. Experts will be looking for the level of IgE antibodies in the blood to determine a diagnosis. Tests will usually return graded with grade 0 being a negative reaction, through to grade 6, which represents a strong positive reaction. The higher the grade, the higher the risk of a reaction to the suspected allergen.
Blood tests can also be used to test an IgE reaction to dust mites, pollens and pets. There are more specific tests for reactions to nuts, seafood, antibiotics, stings, latex etc.
If you are suspected to be suffering a non-IgE allergic reaction, you may be put on a food elimination diet. This will involve the suspected food to be removed from your diet for two to six weeks, before the food slowly being reintroduced. If you notice a recovery during the elimination, only for symptoms to return when reintroducing the food, you may have an allergy or intolerance.
Please do not attempt a food elimination diet without discussing the changes with your GP or a nutrition professional. If you are looking to start the diet, you can find a nutrition professional who resonates with you using our advanced search tool.
A food intolerance is not easy to diagnose, despite being more common than a food allergy. While not life-threatening, symptoms can leave a person feeling unwell and interfere with daily life.
Food intolerance reactions do not involve the immune system and so the workings of many food intolerances are unclear. Symptoms are often delayed, occurring hours later and sometimes lasting a number of days. The symptoms associated with a food intolerance are usually gut-related, such as diarrhoea, bloating, constipation and skin problems, such as eczema. It is common for people with food intolerance to experience multiple symptoms, but not all of these are recognisable. People may experience non-specific symptoms, such as headaches, brain fog and lethargy
As it is possible to be intolerant to more than one food, it can be difficult to determine whether food intolerance is the cause of a chronic illness and which foods are responsible.
Food intolerance can be caused by a number of factors. Certain lifestyles - for example a diet with erratic food intake, lacking nutrients and minerals or a diet high in refined foods with low intake of dietary fibre - can have an effect on how the body reacts to specific food. If you suspect your lifestyle or eating habits may be a factor, you may benefit from seeking professional advice. A nutrition professional will be able to work with you to recognise the foods that may be causing symptoms and offer suggestions to how you can avoid them.
Do I have a food intolerance?
While there are many tests which can help recognise a food intolerance, one of the most popular methods is the food elimination diet.
Types of intolerance
While any type of food can potentially cause an adverse reaction in the body, there are some foods that more commonly cause a reaction than others. Individuals may experience lactose intolerance, gluten intolerance and wheat intolerance. Others may experience an intolerance to naturally occurring food compounds, such as caffeine.
Coeliac disease is an autoimmune disease which causes the individual to be intolerant to the protein, gluten. The severity of symptoms and side effects vary for each individual, but common symptoms include abdominal pain, diarrhoea and bloating.
According to Coeliac UK, the condition affects one in 100 people in the UK, though they estimate nearly half a million people are undiagnosed. In some cases, symptoms can be very mild. This often leads to the condition going undiagnosed, or being misdiagnosed as a food intolerance or another digestive disorder.
Content reviewed by dietitian, Caroline Gillies. All content displayed on Nutritionist Resource is provided for general information purposes only, and should not be treated as a substitute for advice given by your GP or any other healthcare professional.
This is where you can submit feedback about the content of this page.
We review feedback on a monthly basis.
Please note we are unable to provide any personal advice via this feedback form. If you do require further information or advice, please visit the homepage & use the search function to contact a professional directly.
- How to get an accurate allergy test - advice for adults
- Heart health for coeliacs and free from foodies
- Overcoming IBS and digestive problems
- The milk debate: is milk intended for human consumption?
- Give yourself a digestive MOT
- 'Autoimmune' conditions and the gut health
- The basis of anti-inflammatory diet
- How to recognise a food intolerance
- My child has autism: do we need to go gluten and dairy free?
- What are the signs of dairy intolerance?
- Dairy intolerance in adults
- Buckwheat - wheat alternative so great for IBS sufferers
- The problems with food intolerance testing
- Confused about whether to go wheat-free?
- Could you have a food intolerance?
Share your story
If you have been to see a nutritionist, sharing your experience may help others to make a decision about seeking nutritional support.Share your story