Food intolerance includes any adverse reaction to food that occurs from a few hours to a few days after the ingestion of one or more foods,the reaction is not modulated by the immune system but by specific biochemical mechanisms.

Any annoying and harmful reaction that occurs following the ingestion of food can be seen in the vast chapter on adverse food reactions. These reactions are divided into toxic and non-toxic reactions: Toxic reactions are those that occur following the ingestion of toxic substances that contaminate food (metals, additives, insecticides, bacterial toxins, mycotoxins, etc.) and are dose- dependent, they represent food poisoning. The non-toxic reactions are due to hypersensitivity to food, they are unpredictable reactions that affect predisposed subjects and can be genetic or acquired (food allergies and food intolerances).

The disorders related to intolerances are different from those of allergies: they are less acute, they tend to repeat themselves over time and are difficult to link to the intake of a specific food. We are talking, for example, about some of the most common ailments such as fatigue, swelling, headaches, vents on the skin, coughs, rhinitis, asthma.

Intolerances can be of 3 types:

  • Enzymatic intolerances
  • Pharmacological intolerances
  • Indefinite intolerances


They are determined by the lack or poor production of specific enzymes that are essential for metabolizing and making certain food components assimilable.

This defect in the enzymes responsible for the metabolism of certain substances is generally congenital, but can sometimes be acquired over time.

Enzymatic food intolerances are numerous and include a number of diseases that affect the metabolism of carbohydrates, proteins and lipids.

The most frequent enzymatic intolerance is lactose, a substance contained in milk, the most common form of wheat intolerance is celiac disease, another example of intolerance due to an enzyme deficiency is favism. Specifically, for people with disaccharidase defects (carbohydrate metabolism), they have gastrointestinal manifestations that are clinically similar to the symptomatic picture of food allergies. On the edge of intestinal villy there are enzymes that have the task of breaking down disaccharides, such as lactose or sucrose, and oligosaccharides derived from starch digestion.

Disaccharidase enzymes are normally capable of almost complete digestion of disaccharides and oligosaccharides, so much so that only a modest amount of molecules reaches the colon in an undigested form. At the colon level, the bacterial flora transforms these substances into hydrogen, methane, carbon dioxide and into organic acids that help keep the faeces soft and make bowel movements frequent.

In subjects with defects of primary disaccharidases or secondary to a defect of intestinal mucosa, the colon is reached by a greater quantity of undigested sugars and this determines an increase of intestinal fermentations, an excessive production of gas and acids and the presence in the lumen intestinal intake of ingested substances and their metabolites in quantities greater than the absorption capacity of the intestinal wall. In the feces of these subjects there are reducing substances, normally absent, and in the expired air there is hydrogen. The clinical symptoms of the disaccharidase defect are: flatulence, abdominal distension, borborigmas, pains, diarrhea and even nutritional defects and depend on both the amount of sugar ingested and the extent of the enzymatic defect.


They manifest themselves with symptoms similar to those of IgE mediated food allergies, but if laboratory tests and the search for food-specific antibodies are performed, the results are negative. They are usually due to the intake of large quantities of foods containing pharmacologically active substances, including histamine or histamine-liberating substances: tyramine, phenylethylamine (biogenic amines), caffeine, theophylline, alcohol.

There are foods with a high histamine content such as: fermented and seasoned cheeses, fermented beverages (wine, beer), cured meats and sausages, herring, salmon, sardines, anchovies, tuna, preserves, tomatoes, spinach, avocado; and foods that release histamine: tomatoes, strawberries, crustaceans, seafood, egg whites, chocolate, canned foods, meats, pork, aged cheeses, exotic fruits (pineapple, papaya).

The histamine is normally present in the intestinal lumen, it can be of exogenous origin, following the ingestion of foods that contain it, or endogenous, due to its release from cells of the gastrointestinal tract or by the intervention of intestinal flora bacteria .

Some foods with a high content of starch and cellulose, such as starchy foods, legumes and potatoes, intervene on the balance of intestinal flora, stimulating the development of bacteria capable of transforming histamine.

In our body there are powerful defense enzyme systems that determine the transformation of histamine into inactive metabolites, but in some individuals, due to a lack of these mechanisms, ingestion of histamine-rich foods can induce a PAR (pseudo-reactions). allergies) from histamine foods.

Clinically the histamine PAR manifests itself with symptoms similar to those present in IgE mediated food allergies: itching, skin rash, hives; rarely rhinitis, asthma, anaphylactic shock.


Among the histamine-liberating substances we recall the tyramine that derives from tyrosine, which is degraded to an inactive metabolite following the intervention of a monoamine oxidase (MAO). The intestinal tyramine may be exogenous due to the ingestion of foods rich in the substance (cheeses, bananas, avocados) or endogenous for the transformation of tyrosine present in foods ingested with the intervention of tyrosine microbial microbial. In normal subjects the intestinal tyramine is degraded by the MAO of the intestine and liver without any modification of its plasma level, but in individuals in whom there is a condition of primary failure of MAOs or for the ingestion of anti monoamine oxidase drugs or other molecules able to interfere with the activity of these enzymes, for example damaged fish, tyramine is not degraded properly and an excessive amount circulates.

At the clinical level, tyramine PARs manifest themselves with symptoms due to the action the substance has on the vessels and on the nerve endings. You may have tachycardia, hypertension, throbbing headache, fever and flushing of the face and even skin symptoms such as hives.


They occur when an individual shows hyper-reactivity towards substances present in certain foods, such as additives. Each food, at the end of the production and transformation processes, can also contain food additives and, sometimes, contaminants placed unintentionally.

Some individuals may develop intolerances to additives, natural or synthetic molecules used in the food industry in order to improve the appearance and taste of foods and their preservation, permitted by law. The symptoms manifest themselves with itching, hives, rhinitis, asthma, headache and migraine.

The main types of additives are:

  • Dyes, both natural (chlorophyll, carotenoids, anthocyanins) and artificial (such as tartrazine yellow, cochineal red, etc.). Tartrazine yellow, for example, can cause symptoms such as asthma and hives.
  • Preservatives, used to improve food preservation by preventing the growth of bacteria. They can cause intolerances, for example, sulphites (also antioxidants), sorbates, benzoates, p-indrossibezoates, which can cause asthma, nitrites and sodium nitrates, which can lead to headaches and vasodilation.
  • Antioxidants, among which the most used are sulphites in the form of sodium metabisulfite, mainly for the preservation of wines but also present in beer, fruit juices, other beverages, cheeses, dried fruits, sauces; they can give asthma, itching, angioedema, rhinosinusitis.
  • Flavor enhancers, among which the best known and used is sodium glutamate, present in canned meat and broth nuts, which can lead to respiratory crisis, sweating, abdominal cramps.
  • Sweeteners, including the main ones are aspartame, saccharin and sorbitol; the latter, used in candy and chewing gum, can give flatulence and diarrhea, while any toxicity of aspartame is still the subject of controversy and scientific investigation.
  • Thickeners, including gum arabic, used for example in the preparation of sweets, candies, ice creams, preserves, juices, spreadable cheeses, and which can cause eczema, rhinitis and hives.

Additives intolerances are still little known, both about the precise health effects and about the real impact on the population.


A test used for the diagnosis of a pathology should be accurate – that is, to have a close correspondence with the real value that one intends to measure – and precise – or to give reproducible, constant and unequivocal results, on the same sample. Only in these conditions will the results collected be of any use and can be used constructively and useful for the patient.

Unfortunately, many of the tests that are proposed for the diagnosis of food intolerances do not meet these two basic requirements: at best they are tests that have poor accuracy, reduced precision and a strong dependence on the operator’s abilities. At worst, these are real jokes based on pseudoscientific concepts, lacking any validation and usefulness.

It must be emphasized that these tests are not only useless but can even be dangerous. Often in fact, on the basis of these results, we resort to severe elimination diets that in some subjects could lead to deficiencies, while in other situations they could go to mask or confuse symptoms attributable to serious pathologies, making the diagnosis more difficult and making them lose of precious time in the definition of adequate therapy.

Among the tests of doubtful or no use in the diagnosis of food intolerances:


A very widespread test, look for some particular antibodies (Ig4) in the patient’s serum whose presence would indicate a sensitization to specific substances present in some foods. In fact, the available studies indicate that the test has no diagnostic relevance, Ig4 positive towards a particular food are in fact also present in subjects who have never complained of any problem. Moreover the test does not allow to distinguish those subjects that present a true IgE mediated allergy, exposing them to important risks in the case in which the responsible allergens are not correctly identified or attempts are made to reinsert food for which the patient actually presents a real allergy.


A very old test, proposed in the fifties of the last century. It is based on the direct observation of morphological changes affecting white blood cells, once they have been exposed to specific components of food. ALCAT is an automated version of the cytotoxic test. The available data indicate that these are non-reproducible tests, strongly dependent on the operator, with very different results for the same patient in subsequent tests.


Based on the studies of an obscure German scientist, Voll, who would have observed variations in the electrical potential of the skin when a subject comes into contact with harmful or non-tolerated foods. All the equipment used is unconventional, that is, they do not meet precise scientific standards, but have a common function: the subject becomes part of a circuit in which weak electric currents or electromagnetic stimuli are passed. All the studies carried out are in agreement: these tests have no diagnostic validity, the results are completely random and not reproducible. Moreover, there are no data that support the hypothesis of Voll.

  • Bioresonance

Also in this case we work on the hypothesis that the organism emits electromagnetic waves that are altered in case of allergies and intolerances, waves that can be detected, filtered and even rehabilitated and cleaned thanks to specific devices. Clinical studies have shown no diagnostic value.


The theory behind this examination, widely used by chiropractors, foresees that allergy or intolerance can cause an appreciable loss of strength of the subject. During the test, the patient with one hand holds an ampoule containing the substance or food tested and with the other pushes against an operator who records any changes in strength. There are no data to support the method and the very strict dependence on the operator’s impressions undermines its reproducibility at the foundation; moreover, the substance never comes into direct contact with the patient, so any reaction becomes really difficult to explain in a rational manner. And let’s face it, doing strength tests while holding glass ampoules containing allergens doesn’t seem like an infallible diagnostic method.


The patient is exposed directly, at an intradermal or sublingual level, to the allergen, thus evaluating every possible type of reaction that appears in the next ten to twelve minutes. A variant that combines the principles of this test with those of applied kinesiology is the DRIA test. A standardization is lacking, reproducibility is not verified and the range and subjectivity of the possible interpretations are really very wide. Furthermore, direct exposure to the antigen could be extremely dangerous in the case of highly allergic individuals.


Often proposed to evaluate heavy metal intoxication which, according to proponents, could be the cause of food allergies and intolerances. All the studies and data collected show a lack of precision and reproducibility of this type of exam.


    It is based on the hypothesis that contact with food in relation to which intolerance exists may cause changes in heart rate. An increase in heart rate of about 10 beats per minute would indicate positivity. Obviously there is no scientific evidence to support this hypothesis and the strong dependence on the patient’s emotion and on the operator’s abilities is evident. This is only a small sample of the great variety of tests offered. It is clear that in many cases it is either very old tests, based on observations that are difficult to reproduce, or tests used improperly, the case of Ig4 detection, or pure fantasy tests, based on pseudoscientific theories cloaked in some kind of credibility thanks to the use of machinery that may appear more or less sophisticated. If then in the name of the test the term “quantum”, “emotional” or “energetic” appears you can be reasonably sure of being faced with a completely useless examination, if what you are looking for is a serious diagnosis.


Obviously there are also reliable, safe, precise and reproducible tests, useful in the diagnosis of intolerances and allergies.

For allergies, conditions that can potentially put the patient’s life at risk, there are very precise and standardized diagnostic paths, to be carried out exclusively under medical supervision. If an allergy is suspected, it is always necessary to consult an allergist who can identify the appropriate diagnostic tools.

Even for intolerances it is well to avoid self-diagnosis, which is so fashionable today, and refer firstly to your doctor and therefore to specialists able to prescribe any necessary tests.


.For celiac disease, there are first-level tests based on the search for specific antibodies in the patient’s serum:

  • dosage of IgA antibodies against tissue transglutaminase (screening test)
  • anti-endomysial antibody dosage (confirmation test)
  • dosing of IgA and IgG antibodies against deamidated peptides of gliadin (tests for the pediatric band and for monitoring subjects in aglutinate diet)

A test that has a negative predictive value can help to exclude the presence of the disease, but the evaluation of the HLA genetic structure is poor, with the search for the presence of some genetic variants predisposing to celiac disease. In the absence of such variants it is highly unlikely that the subject will suffer from this condition. The test is very useful in assessing the genetic predisposition of first degree relatives of celiac subjects.

Discriminant tests in the adult subject are the esophagus-gastro-duodenoscopy duodeno-jejunal biopsies, tests that confirm the diagnosis thanks to the direct observation of the lesions at the level of the mucosa of the digestive system.

For nickel allergy the patch test is used which consists in placing a preparation containing nickel in direct contact with the skin. If a systemic nickel syndrome is suspected, after having verified the positivity to the patch test, it is necessary to proceed with an exclusion diet, very complex and difficult, followed by a provocation test.

The lactose breath test is used to diagnose lactose intolerance. During the test the patient takes a standardized dose of lactose: at successive time intervals the expired gases are analyzed in search of hydrogen peaks, whose presence indicates intestinal fermentation of undigested lactose.

The breath test can also be performed to evaluate the lack of absorption of other sugars such as lactulose, xylose, fructose or sorbitol. These tests can either detect difficulties in absorbing specific sugars or indicate the presence of bacterial contamination in the small intestine or identify alterations in intestinal transit. The method of execution is similar to that of the lactose test, with the measurement of the hydrogen present in the patient’s breath at defined time intervals after the consumption of a standard dose of the sugar in question.

The diagnosis of pharmacological intolerance is essentially anamnestic, while for intolerances from undefined mechanisms the Provocation Test, ie the administration of the suspected additive (nitrites, benzoates, sulphites, etc.) may be useful. In summary, the diagnostic procedure of a patient with suspected food intolerance should include a multidisciplinary approach that involves the allergist specialist, gastroenterologist, step by step, to exclude gastrointestinal and possibly dietary pathologies, to correct dietary habits.


To overcome food intolerances it is imperative not to exclude foods that disturb (choice that can have meaning only in gluten and lactose intolerance, two intolerances diagnosed among other things only with specific medical analyzes), but integrate them step by step within a mid-week food rotation plan appropriately designed and individualized

The goal in the treatment of intolerances is not to eliminate food forever, but to progressively reintroduce it without negative effects. It consists in a plan of continuous elimination and reintroduction of the food responsible for the symptoms of food intolerance. The classic program provides 3 days of abstinence from non-tolerated food, and clearly from all those belonging to the same group, then reintroduction on the fourth day.

Below is an example:

from the 1st to the 3rd day complete elimination of non-tolerated food;

4th day free intake of all foods and moderate reintroduction;

5th – 8th day still absolute suspension of the food that caused the symptoms;

9th day free diet without limitations and still moderate reintroduction;

10 – 13th day new suspension diet.

After 10-12 days of rotating diet the body will be detoxified so it will be possible to insert a new food every 24h.

If there will be any symptoms appear for at least 3 days do not introduce new foods to allow the body to detoxify.

With this type of diet within 4 weeks it will be possible to determine the food or foods to which you are intolerant and with a total abstinence that varies from 2 months to a year you will have detoxification of the organism and you can then reintroduce the food “incriminated” without being recognized as a stranger.

The positive effects of the rotation diet are two:

The rotation diet, unlike the elimination diet, controls inflammatory reactions while maintaining a minimum tolerance towards the food that creates disturbance

The alternation of free meals and days of cleansing diet helps the body to rebuild a tolerance towards the substances that cause the symptoms

Here are 3 positive signs:

1) Digestion improves

2) Swellings and meteorism decrease

3) Improves mood: The intestine is defined as “Second brain”, this is because the enteric system is closely related to the nervous system. Any discomfort in the intestine (and not only) therefore affects one’s mood and vice versa


An alternative to the rotating diet is the diet excluding Dr. Rinkell, which provides for the total exclusion of only one food at a time, including naturally foods from the same family or group, for at least 15 days. After 14 days we have to make a health check; if we actually feel better it will be good to continue abstinence for at least 4 weeks before reintroducing the food in small quantities. Self-administered, inappropriate and restrictive exclusion diets can carry a non-negligible nutritional risk and, in children, poor growth and malnutrition. They can also manifest eating disorders. When undertaking an exclusion diet, even for a single food or food group, specific nutritional indications must be provided, to ensure adequate caloric intake and, macro and micronutrients. The diet must be managed and monitored by a competent professional to identify nutritional deficits early and, in children, verify that growth is regular.


Lactose is a disaccharide synthesized by the mammary glands of all mammals and consists of the monosaccharides glucose and galactose. The term lactose intolerance defines the reduced digestive capacity of the disaccharide from the small intestine due to a poor production of the enzyme lactase, located in the brush border of the enterocyte. Only a congenital deficiency of lactase is rarely observed; in most cases, in fact, the enzyme is present at birth and its quantity remains high in the first year of life. After weaning, a rapid decrease in lactase activity is observed; this loss of functionality is more drastic in some populations than in others. Milk allergy and lactose intolerance are fairly common conditions, but there is often a tendency to confuse and confuse them with one another. Lactose intolerance is a disease that causes gastrointestinal disorders (abdominal color, swelling, abdominal cramps, intestinal disorders) following the consumption of milk and dairy products. This is a non-allergic reaction, that is, a reaction that does not affect the immune system. Cow’s milk allergy, on the other hand, is due to the presence of IgE antibodies against some milk proteins, which the immune system develops following sensitization. In cow’s milk allergy, even small quantities can cause allergic reactions, including severe skin, gastro-intestinal, respiratory or anaphylactic. Lactose intolerance is classified as primary or secondary. Primary lactose intolerance is defined as the condition for which the body does not produce lactase due to a genetic modification. In case of primary lactose intolerance the symptoms appear already in the first years of life. One speaks of secondary lactose intolerance instead when it occurs in the course of life, due to a deficit – sometimes transitory – of the enzyme, which can be caused by lesions of the gastrointestinal tract, by sudden changes in the diet or by infections of the gastrointestinal tract. Lactose consumption in subjects with lactase deficiency can cause diarrhea, abdominal cramps and pain, abdominal tension and flatulence. The clinical effects are closely related to the dose and there is a wide individual variability.

The symptoms are caused by undigested lactose which, reaching the colon, draws water due to an osmotic action causing diarrheal phenomena; moreover, the disaccharide is an excellent substrate for the fermentation of intestinal bacterial flora with consequent production of gas and other osmotically active substances that contribute to determining the clinical manifestations.

If symptoms are present, intolerance can easily be unmasked by the so-called breath test or breath test. Through this examination the concentration of hydrogen in the exhaled air is evaluated after a lactose load. Since the fermentation of undigested sugar produces hydrogen which is readily reabsorbed by the intestinal walls and eliminated by respiration, in the case of lactose intolerance, a peak concentration of hydrogen is observed in the expired air.

To allow the use of milk also to all those who suffer from intolerances against it, there are milk lactose-free milks in which lactose is found, for the most part (70-75%), hydrolyzed, that is already broken down into glucose and galactose. Alternatively, you can “settle” for soy milk or rice milk. Even yogurt, thanks to the fermentation of lactose made from the ferments it contains, is generally well tolerated.

However, we must not forget that there is no threshold dose valid for everyone and therefore lactose tolerance is absolutely subjective. The excellent therapy for lactose intolerance is a diet that includes a reduced intake of foods rich in lactose (butter, milk, dairy products, fresh cheeses, biscuits with milk or butter, milk chocolate, ice cream, etc.). The reduction of these foods can be done gradually in order to verify the tolerance threshold of the subject.


Gluten sensitivity (Gluten Sensitivity), which is estimated to interest from 6 to 8% of the population, is a chronic condition that manifests itself with more or less marked intestinal or extraintestinal symptoms, linked to the ingestion of gluten.

Gluten Sensitivity is the condition in which following the ingestion of gluten we are in the presence of symptoms largely comparable to those of celiac disease and irritable bowel syndrome (swelling, drowsiness, diarrhea, constipation, abdominal pain, headache, depression, etc. ) but there is no atrophy of the intestinal villi or autoimmune response of the organism. Gluten intolerance can come out at any age and is increasingly widespread, it seems among other things that many people suffer from it without knowing it. This happens because we underestimate some symptoms that can come out at any age and that often do not connect easily with this type of intolerance.

The diagnosis of Gluten Sensitivity is currently a diagnosis of exclusion, characterized, that is, by the negativity of the immunological tests for wheat allergy (IgE class antibodies directed to wheat and PRICK test), by the negativity for the typical celiac disease ( antiendomysium and antitransglutaminase antibodies) and from a normal intestinal biopsy or with minimal alterations.

The symptoms that appear most frequently in the case of gluten intolerance are:

  1. Digestive problems: you can feel swelling, belly air and suffer from diarrhea or constipation. In the case of constipation, it is necessary to pay particular attention to children noting if the problem appears above all after eating gluten.
  2. Keratosis pilare, also known as “chicken skin” which mainly affects the back of the arms. This could indicate a lack of fatty acids and vitamin A, due to the malabsorption of these nutrients caused by gluten in the intestine.
  3. Feelings of tiredness, fatigue, fog in the brain or a particular psycho-physical feeling of weight after eating a meal containing gluten.
  4. Neurological symptoms such as dizziness, a feeling of losing your balance, dizziness until you come to real fainting. But also anxiety, depression or mood swings.
  5. Migraine, headache: it is necessary to exclude the presence of other pathologies, periods of stress, premenstrual syndrome or other situations in which this symptom may appear.
  6. Hormonal imbalances, such as very strong pre-menstrual syndrome, polycystic ovary syndrome or unexplained infertility.
  7. Inflammation, swelling or pain in the joints (not due to current trauma or disease) such as to the fingers, knees or hips.

Celiac disease and gluten intolerance are two different pathologies. In people with celiac disease, gluten triggers an autoimmune reaction, which attacks the intestine and severely damages the intestinal mucosa. Gluten intolerance, ‘glutensensitivity’, instead manifests itself with abdominal pain, irritable bowel, headache, but does not involve severe intestinal injuries. Celiac is always sensitive even to small quantities of gluten, while the intolerant has a higher resistance threshold and also enjoys transitory moments of well-being, in which symptoms do not manifest themselves at all. Sufferers of Gluten Sensitivity have a defect in innate immunity, therefore they react in a few hours to gluten, perceived as an enemy protein. In celiac disease the damage and the consequent reaction of the body can instead take place after months, in many cases after years.