Do you have a food allergy or intolerance? Victoria Bittle has kindly offered to write this blog post, to help to distinguish between each diagnosis, to describe how you might be tested and what you should do if you think you have one.
Thank you Victoria 🙂

If I had a dollar for every time I heard ‘I don’t tolerate that’ I’d be rich by now! Each year visits to GP’s for reported gut, skin or respiratory symptoms increase. Is food allergy and intolerance becoming more of an epidemic or are we just becoming better at recognising and treating it??  Many people often get confused about the differences between allergy and food intolerance and often they can present in similar ways, which can be confusing.

So what are the differences between allergy and intolerance?

Surprisingly, true food allergy is rare; affecting approximately 2% of the adult UK population and 8% of children (  Food allergy involves the immune system, where the body sees the food as a foreign body and makes specific antibodies (IgE) to fight off the potential harmful allergen. This results in a release of histamine and it’s the release of this, and other chemicals that cause the symptoms, we recognise as an ‘allergic reaction’. This reaction tends to happen relatively quickly following exposure to the allergen (the particular food) making it slightly easier to identify the cause. Common symptoms include wheezing, difficulties breathing, a running nose, vomiting, diarrhoea, skin rash, itching or swelling.

Most-Common Food Allergens

Food intolerance is a little ‘wooly’ and not as clear cut as a food allergy.

Food intolerance reactions do not involve the immune system and reactions tend to be more delayed occurring hours to days after exposure. Symptoms vary however, more commonly associated with gut (bloating, constipation, diarrhea) and skin problems such as eczema.

Lactose Intolerance

People often talk about being intolerant to lactose/wheat or that they may be sensitive to caffeine or natural occurring histamine foods such as cheese, wine, or pickled foods. Having primary lactose intolerance is actually rare; this is when you lack the enzyme lactase meaning they are unable to break down the natural sugar within milk (lactose). More commonly seen is secondary lactose intolerance, which tends to be more temporary and can occur post gastrointestinal bugs/antibiotics. A simple lactose free diet (exclusion) for 6-8 weeks with re-introduction period tends to restore tolerance again.

Unlike with a true allergy, a positive lifestyle changes such as exercise, a regular meal pattern, a nutrient dense diet and a reduced amount of fatty and processed foods can significantly impact your food tolerance.

It’s therefore important you look at making positive changes to your diet and lifestyle first before you start eliminating foods unnecessarily.

How do I find out if I’m allergic?

If you suspect an allergy based on the above information it is recommended that you visit your GP who can refer you onto the appropriate service for specific testing and dietetic input, should it be necessary. Tests that help to confirm an allergy include, a Skin Prick Test; which involves pricking the skin with an allergen, this may cause a localised response (i.e. redness, swelling). A Specific IgE blood test (previously known as RAST) is another way to test an allergy, it measures the amount of IgE, an antibody that increases in the blood in response to a (suspected) food. The results are not always reliable in both examples; therefore, an oral food challenge remains the gold standard for allergy testing. These can be performed either at home if appropriate or in the hospital setting under supervision from a specialist medical team and dietitian.

How do I find out if I am intolerant?

Unfortunately, there aren’t many validated tests that can confirm intolerances, therefore for that reason the gold standard is to exclude the specific food for a period of time and then re-introduce it to see if symptoms reappear/worsen. A food and symptom dairy can be an extremely useful tool to help you to identify culprit foods and a dietitian can provide a tailored elimination diet to suit your needs. Dietitians are important during elimination diets to help advise you on a nutritionally complete diet including meals and snacks and special ‘free from products’ to ensure you can still enjoy, as well as stick to your diet.

In Summary

Food allergies and intolerances do appear to be all around us, so If you suspect an allergy or intolerance, make sure you go down the right channels in order to get the correct diagnosis and support you need. Speak to a qualified health professional; e.g. your GP and be skeptical of any ‘allergy’ test that’s either different from those described above and/or offered by a non-medic/doctor. Restricting your diet without supervision from a qualified dietitian may be difficult but also very dangerous if your diet isn’t nutritionally adequate, a dietitian can support you in finding replacement ‘free-from’ foods to prevent this from happening.

Top Tips


– Keep a food and symptom diary

– Alter your diet and lifestyle to ensure it is balanced and healthy

– Once you see notice patterns in your food diary, visit the GP who can advise and refer you on to a specialist if needed

– See a dietitian if you are excluding a number of foods for expert advice and to ensure you aren’t missing out on the key nutrients your body needs to stay healthy.


For more information on allergy and food intolerances visit Allergy UK.

Victoria Bittle

The Author – Victoria Bittle is Paediatric Ketogenic dietitian at Guy’s and St Thomas’​ NHS Foundation Trust

Victoria is an experienced Dietitian, specialising in paediatric allergies and weight loss working predominantly within the NHS. In her spare time she try’s and reviews ‘free from’ products on the website Allergy Angle and works privately with the Diet Angles too. Victoria’s skills help assess, educate and treat nutritional related problems and her friendly, practical and professional approach aids motivation to achieve the desired goals and outcome.

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