Food Allergy or Food Intolerance? What's the difference?

Lorisian, a laboratory with 35 years of experience in food intolerance testing has collected quite a lot of data over the years, and states that about 45% among us are suffering from a food intolerance. I get a lot of calls from clients enquiring about food intolerance testing, and in many cases I recommend testing, but within just a few minutes of talking to the client it often turns out that what they are experiencing is more likely to be a food allergy, not a food intolerance. So, what’s the difference?


First of all, unlike food intolerances, food allergies are quite rare: only about 2% of the population suffers from them. Typically, food allergy symptoms occur very soon after ingestion of the offending food, and for that reason many sufferers don’t even need a test. They often are aware what it was that caused the reaction. Nevertheless, testing is recommended, because if we are allergic to one food there can be cross-reactions with other foods, too.

If you have a food allergy, your immune system is mistaking food or drink compounds as harmful and produces IgE (immunoglobulin E) antibodies to fight what it perceives as an invasion. This causes an inflammatory response, and typical symptoms are swelling of the tongue and/or skin, rashes, itching, runny nose and/eyes, difficulty breathing and potentially anaphylactic shock, which can even be fatal. If you think that you have a food allergy, it is important that you see your doctor to get tested for IgE antibodies. Should you test positive for one or more foods, you must avoid those for life.

Food intolerance is quite different. Symptoms are less severe, but more diverse, often – but not always – gut-related: indigestion, acid reflux, bloating, flatulence, stomach pains, diarrhoea or constipation are common. However, joint pain, tiredness, but also insomnia, migraines and headaches, weight gain or difficulty to lose weight, acne, eczema and itching can all be down to food intolerance. Everyone is different, and those who suffer from food intolerance tend to react to a combination of different foods or drinks.

Reaction onset is usually delayed, up to 72 hours. This is what makes it very difficult for sufferers to work out which food it is that causes problems. The best way to find out it to eliminate suspect foods for three to four weeks and then to reintroduce them one by one to see if a reaction occurs.

Unlike food allergy, food intolerances can have a number of different underlying reasons, such as

  • Coeliac Disease, an autoimmune disease which is triggered by an intolerance to gluten, a protein in certain grains. Gluten proteins damage the intestinal lining and prevents nutrients being properly absorbed. Coeliac sufferers (about 1% of the population) must avoid gluten for life.
  • Enzyme deficiencies – e. g. lactose intolerance, in which sufferers lack the enzyme lactase, which is needed to break down lactose, the sugar in milk. It is thought that about 75% of the world population stop producing lactase after weaning.
  • Chemical sensitivities to food additives, e. g. food colouring (tartrazine – yellow – E102; sunset yellow E110) or caffeine.
  • Histamine Reactions – when you seem to react to ‘everything’, with no apparent rhyme or reason, even healthy foods such as fermented vegetables or drinks (sauerkraut, kimchi, kombucha) it is worth considering histamine intolerance.
  • IgG antibody reaction, another immune reaction, but one that involves a different type of antibody: immunoglobulin G (IgG). This happens when partially digested proteins from food or drink penetrate the gut wall and enter the blood stream – which they shouldn’t be able to. The fact that they can suggests that the intestinal lining is compromised, a condition often referred to as ‘leaky gut’. The gut wall can suffer damage for a variety of reasons: stress, medication, infection, an imbalance between good and bad bacteria or yeast overgrowth, physical trauma after an accident or operation. If you test positive for IgG antibodies, avoiding the offending foods is just the first step. You should also consider a gut repair programme. The good news is that unlike in the case of a food allergy, foods may be reintroduced in the future without causing any further problems, avoidance need not be lifelong.