Skip to main content

In the UK, 20-30% of people perceive themselves to have an intolerance or allergy

Our food is mass produced and grown quickly, so there are more potential immunologically active proteins in our food system

A growing number of people are diagnosing themselves with food intolerances and are helping to sustain a huge surge in free foods on the market. Is it just a fad or are allergies and intolerances really on the rise? Is there a difference between the two? Dietitian Linia Patel reports.

Defining differences

Food allergies and intolerances are often confused, as their symptoms can seem similar. In fact, the two are quite different and it’s important to get familiarised with the two:

  • food allergy involves the immune system and happens when the body reacts to a protein in specific foods, which are usually harmless. Reactions are usually immediate and can occur after being exposed to very small amounts of the food. Symptoms of an allergic reaction manifest in many ways, such as rashes, itching, hives and swelling and, when severe, can lead to serious trouble breathing and death. The most common food allergies include eggs, peanuts, soy, milk, wheat, fish and shellfish1,2. Food allergies affect around one in 20 children and two in 100 adults in the UK. Up to 10% of babies may suffer from food allergies but most of these will grow out of the allergy early in life3.
  • A food intoleranceon the other hand, does not involve the immune system; however, it is a chemical reaction that is triggered from substances that naturally occur in foods (such as lactose or gluten) or that arise in food processing methods (such as preservatives, artificial colours and flavourings). Reactions are dose dependent and different people will tolerate different amounts of any given chemical. The most common intolerances include lactose, histamine, tartrazine (artificial food colour), sulphites (preservative), monosodium glutamate (MSG) and, increasingly, gluten. An intolerance to food is rarely life threatening and tends to occur hours or days after the food is eaten. Symptoms are generally described as an unpleasant reaction to a particular food, involving tummy craps, flatulence, vomiting and diarrhoea1,2. In the UK, 20-30% of people perceive themselves to have an intolerance or an allergy to one or more foods3.

Why the rise in allergies and intolerances?

There is no single explanation for why we are becoming more allergic to food. However, science has some theories, which include1,2,4:

  • Vitamin D deficiency: Most populations around the world are spending less time in the sun or using sunscreen, which affects how much vitamin D we make and have in store in our bodies. Reduced production and increased body fat levels (fat traps vitamin D, making it unavailable for use) mean that the majority of people are vitamin D deficient. Vitamin D is vital in helping us develop a healthy immune system, hence a deficiency makes us more susceptible to allergies.
  • Too many antibiotics and pesticides: A healthy and diverse gut microbiota is key to developing a strong immune system as this decreases the likelihood of intestinal permeability, which makes us more prone to allergies. It is believed the increased exposure to antibiotics and pesticides within the western world, as well as diets low in fibre, is taking our intestinal flora out of balance.
  • Hygiene hypothesis: Many studies have shown that, in countries where there is more exposure to dirt and parasites, there is a significantly lower risk of allergies. Parasitic infections in particular are normally fought by the same mechanism involved in tackling allergies. With fewer parasites to fight, the immune system turns against things that should be harmless like food. It seems that the earlier your immune system has to deal with pathogens, the better it develops immunity.
  • Changed farming practices: Compared to 100 years ago our farming practices have changed and, as a result, the quality of the food we are eating has also been affected. Our food is mass produced and grown in the quickest way possible, which means there are more potential immunologically active proteins in our food system, hence increasing the potential for allergic reactions. This is the same with environmental toxins.

Testing testing

Herein lies another big difference between food allergy and food intolerance. There is a valid and reliable way to test and diagnose food allergies. However, there isn’t for food intolerances (sorry guys!)5.

To diagnose food allergies currently, medics use skin tests, patch tests and blood tests to begin diagnosing a food allergy. However, none of these methods stands alone for a diagnosis. The results from these tests must be taken into consideration with the patient’s medical history and must be confirmed by an oral challenge, which is the gold standard in diagnosing a food allergy. In the oral challenge, the suspected food is removed for a period of time with an elimination diet (in conjunction with a dietitian) and then reintroduced. The reintroduction process varies based on the severity of the suspected allergic reaction, how many foods are suspected to cause an allergic response and the results from previous allergy tests. Due to the risk associated with an oral food challenge, it should not be attempted independently but either under medical supervision or with medical approval2,5.

Unfortunately, with intolerances (apart from lactose) there are no blood, breath or stool tests that can accurately determine food intolerances. As tempting and promising as these tests claim to be – and as much as you just want answers – for now, the science says it’s best to save your money! Personalised nutrition is where the nutrition world is moving; however, we are not there just yet. If you suspect you have an intolerance, I would recommend getting in touch with a dietitian or registered dietitian to work out a bespoke plan for you. While you wait for an appointment, keep a very specific food diary of what food you eat when and what symptoms you feel after you eat certain foods5.

About the author

Linia Patel

Linia Patel has a BSc degree in biochemistry and physiology. Since graduating in 2006, Linia has become a leading dietitian and sports nutritionist. She is currently a PhD candidate in public health. Her passion is translating nutritional science into easy-to-digest and practical advice.


  1. Joneja JV (2013), The Health Professional’s Guide to Food Allergies and Intolerances, Chicago, Illinois; Academy of Nutrition and Dietetics.
  2. Guandalini S (2011), Differentiating food allergies from food intolerances: 426-34.
  3. Food Allergy Research & Education (2019, February), Facts and Statistics, retrieved from, accessed on 7 May 2020.
  4. Seth D et al (2020), Food allergy: A review, Pediatr Ann., 1:49 (1).
  5. Turnbull J (2015), Review article on the diagnosis and management of food allergy and food intolerance, Aliment Pharmacol Ther., 41(1): 3-25.

Want to read more from Linia, click HERE to read about how to become portion wise