Food Allergies and Intolerances: What is the difference?

Food Allergies and Intolerances
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We often hear about allergies and intolerances as if they were synonymous but, in reality, these are two very distinct situations and the two terms indicate two different ways of the body to react to foreign substances.

The real incidence of food allergies in adults is 1-2% while food intolerances affect a somewhat larger percentage of the population (about 5 out of 10 people). However, it is not easy to estimate a precise incidence given the considerable variety of symptoms, diagnosis and individual variation of tolerance to symptoms.

Both the American Academy of Allergy and Immunology and the European Academy of Allergology and Clinical Immunology have decided to reserve for the term allergy all those disorders mediated by immunological mechanisms. These include the production of antibodies which, in turn, determine the release of organic molecules (histamine in the first place) responsible for the onset of symptoms such as itching, coughing, breathlessness up to much more serious reactions (even at death if you do not intervene quickly). At the term intolerance, on the other hand, all those disorders not mediated by these mechanisms are reserved. Therefore, food intolerance does not involve the immune system and can be caused by enzymatic or receptor deficiencies that, causing alterations in the absorption of nutrients, trigger the typical symptoms (usually affecting the gastro-intestinal system such as nausea, diarrhea, vomiting, abdominal cramps and, sometimes, even of the skin).

Food allergies

A food allergy is an adverse reaction to one or more molecules (called allergens or antigens), contained in a food, that the immune system recognizes as foreign.
The most frequent food allergies are due to allergens present in foods such as cow's milk, soy, cashews, hazelnuts, nuts, peanuts, shrimps, clams, eggs, wheat and some additives that behave as chemical allergens triggering the immune reaction.
Allergies involve an instant reaction to ingested food and are not dose-dependent. Therefore, people allergic to one or more of these foods cannot touch even a small amount without presenting more or less serious disorders.
The incidence of allergies, as already mentioned, is quite low and is higher in children and infants (7-8%). The most common childhood allergies are those to egg and cow's milk but, in most cases, it tends to resolve with growth (between 3 and 5 years). The allergy to nuts / nuts, on the other hand, tends to remain for life. The most dangerous allergy is that to peanuts that can be lethal if you do not intervene in time.
Usually in food allergies there is a kind of "predisposition"; the presence of one or more allergic family members is a risk factor! This factor increases if both parents have food allergies.
According to some studies, breastfeeding would reduce the risk of food allergy and microbiota problems (compared with artificial feeding).

Food Intolerances

Intolerance, as mentioned above, is a reaction that does not directly involve the immune system and can be caused by enzymatic or receptor deficiencies that cause alterations in the absorption of nutrients.
The most common enzyme defect intolerance is lactose intolerance. Lactose is the main sugar (disaccharide) of milk that is divided into glucose and galactose (monosaccharides) thanks to the enzyme lactase (or beta galactosidase) which allows proper digestion at the level of the small intestine.
In cases of lactose intolerance, the activity of this enzyme is reduced: lactose arrives intact in the large intestine and undergoes fermentation by the bacteria present here. This results in symptoms such as flatulence, cramps and diarrhea, nausea and, in some cases, vomiting.
The solution is to avoid foods containing lactose or take advantage of the help of lactose-free foods. In severe cases, it is good to avoid all those products that contain lactose even in traces (such as some sausages, biscuits and many packaged or baked goods).
Lactose intolerance generally arises in adulthood and should not be confused with cow's milk protein allergy (APLV) which is an immune reaction to one or more cow's milk proteins (especially casein and β-lactoglobulin). This reaction is found in a number of newborns between 0.5 and 4% and decreases with age.
To make a diagnosis of lactose intolerance, since the symptoms are gastrointestinal and, therefore, common to several other situations, it is necessary to carry out the Breath Test (one of the very few tests for valid intolerances).

Other Types of Intolerances

There are also other intolerances that are rarer but, in particularly susceptible individuals, can cause episodes due to "accumulation" due to high and / or repeated consumption: this causes the appearance of symptoms ranging from urticaria to abdominal pain, from diarrhea to headaches, up to arrive, in very rare cases, to reactions of considerable severity.
Among the substances involved we have:

- Histamine (which can also lead to mackerel syndrome)
- Xanthines (theobromine, caffeine, theophylline): can cause insomnia, tachycardia, migraine, nausea and/or reflux.
- Sulphites (used as antioxidants and preservatives in wines, soups, juices and beverages)
- Salicylates (also present in some fruits and vegetables) can also lead to asthma-like episodes.
- Monosodium glutamate: involves an intolerance also referred to as "Chinese restaurant syndrome" that mainly affects the gastrointestinal tract.
However, there is still no scientific validity on this intolerance and on the tests to diagnose it. Several scholars associate the symptomatology with the occasionality or excess typical of when going to certain restaurants.

Finally there are situations such as galactosemia and the amino acid diseases phenylketonuria and tyrosinemia that are rare "intolerances". If not recognized in time, they can be dangerous for the development of the newborn.

Celiac disease: Intolerance or Allergy?

Celiac disease is an intolerance that, to date, is the best known (a bit 'also for fashion). Celiac disease is a bit of an exception to what was said above: despite being mediated by the immune system, it can be characterized by onset, evolution and symptomatology very different from other food allergies. So we talk about permanent intolerance to gluten (to the gliadine fraction) and should not be confused with wheat allergy or with non-celiac gluten hypersensitivity. The latter does not seem to involve the immune system and is characterized by several symptoms (intestinal and extra-intestinal) that seem to improve, until the total disappearance, minimizing the introduction of gluten into the diet. There are several conflicting studies on the subject and the biggest problem is that many subjects make a self-diagnosis of this sensitivity by eliminating gluten without ratio. We will talk about non-celiac gluten sensitivity in a future article in more depth way.

Let's not forget that many problems, intestinal and not, are also due to a strong state of intestinal dysbiosis. So it is not said that there is a real intolerance: for this reason it is good to contact an experienced professional in the field before spending a lot of money on dozens of often useless exams.

Even the symptoms often associated with yeast (swelling, flatulence, alteration of the alvo and brain fog) are almost always associated with intestinal dysbiosis. Before blaming bread, pizza, focaccia, even before self-diagnosing an intolerance to yeast, before spending money on texts that are not scientifically valid, evaluate with the reference professional to work on a possible dysbiosis. In particular, the increase in the genera Aspergillus, Candida, Penicillium is associated with the grafting of imbalance, but it is enough to restore it through nutrition and the use of appropriate supplements to observe the disappearance of symptoms.

Test For Food Intolerances

There is a very large market for tests that should diagnose intolerances but, unfortunately, only a few of these tests are really useful and are supported by scientific evidence. To learn more about the topic I invite you to read the article on Tests for intolerances


1. The American Academy of Allergy, Asthma & Immunology: AAAAI
2. The European Academy of Allergy and Clinical Immunology, EAACI
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Curated by
Dott.ssa Patalano Myriam Biologist Nutritionist

Ischia Nutrizione Patalano