In children with developmental problems, mostly from the autism spectrum, the most common problems are permeable bowel syndrome , high levels of histamine, which is also associated with intestinal permeability, low serotonin levels and high dopamine levels. 97% of serotonin is produced in the gut.

It is worth mentioning that children have physiological intestinal permeability up to two years of age. Their intestinal microflora is different, and if the feces of such a small child are tested, it would not be certain that this condition is pathological. It is not known what the other parameters should be, it cannot and should not be diagnosed by only one parameter. Babies often suffer from stomach upsets, digestive problems, colic, diarrhea, constipation ... These conditions cannot be tested in connection with retardation, because very often we still do not know at this age whether the child has developmental problems. However, high levels of histamine are not physiological.
There are also many children who do not have behavioral disorders or lag behind in their intellectual development, the emotional sphere is also without problems, but research shows the same results as in children with autism spectrum disorders. Rash, swelling, severe allergic reactions are often observed. Intestinal function is also associated with allergies. If a child (and not only a child, there are adults with similar problems) has an allergy to pollen, plants, the manifestation will be redness of the eyes, skin, itching ... This is an indication of high levels of histamine.

In general, histamineis responsible for all types of allergies. It is part of the body's immune response. Any inflammation of the body is an indication of elevated levels of histamine. What exactly needs to be tested in a laboratory depends on the specific complaints of each individual. Things are very subjective. For example, when visiting an Asian restaurant or eating too spicy food, you may have stomach upsets, pain, gas, but this is not a reason to diagnose pathology in the condition. Histamine is elevated in this case, but this will not be a problem, as the body will metabolize it properly and adjust the levels. In some children, the body cannot handle the metabolism of histamine and this can lead to behavioral problems. In plant allergies and allergies in general to contact with "foreign matter", histamine causes local inflammation - redness rash. But when eating foods that we are intolerant to, it causes intestinal permeability, which often leads to problems. Of course, this does not apply to everyone.
Histamine is also responsible for inflammation and can upset the hormonal balance in the body.

Any intestinal inflammationwill reduce the production of serotonin, and if it is too low it is likely to cause a delay in mental development - 97% of it is produced in the intestine. The exact determination of serotonin reference values ​​in the intestinal microflora is still the subject of scientific research. Some children with autism spectrum disorders have very high levels of serotonin. The reasons for them are extremely different. Something that is often observed in them are high levels of dopamine. It is not yet known exactly what the correlation is, but it is one of the possible causes of the disorder. Scientists are not sure why dopamine is so high in children with developmental disorders. High dopamine is also observed in completely healthy children. High dopamine levels are thought to be a hypothetical culprit for stereotypical movements in autistic children.

Histamine and serotonin are important, but dopamine also plays an important role in neurological health. Research on the subject has not been completed and is still ongoing. Of all the children studied in Dr. Rosler's laboratories, the most common were high levels of histamine, low serotonin, and elevated dopamine levels. In such cases, it is most often recommended to eliminate histamine-containing products from the menu.

In addition to histamine, there may be other causes such as inflammation in the intestinal flora - dysbiosis, gluten intolerance, fungal infection and others. Histamine is just one part of the puzzle.

In these cases, the diet plays an important role , which is very different from the generally accepted notions of diet. Gluten plays a significant role in the permeable intestines. There are four different variations of the problem with gluten. On the one hand there is an allergy to gluten, there is celiac disease, which is an autoimmune disease and on the other hand wheat allergy, which is an allergic reaction of the first type (anaphylaxis) and due to massive mast cell degranulation and secretion of large amounts of IgE antibodies - symptoms include life-threatening bronchospasm, edema, abdominal pain and diarrhea, hypotension, urticaria, etc.

Gluten intolerance is not as severe as autoimmune disease, but today people are generally familiar with the symptoms, which are identical in all cases. Symptoms include frequent diarrhea or constipation, whitish faeces with a foul odor, nausea, vomiting, chronic fatigue, difficulty concentrating, and flatulence. There is also gluten-sensitive enteropathy.

The treatment is carried out through a lifelong gluten-free diet - exclusion of foods derived from wheat, as well as secondary treatment with appropriate supplementation as a dietary supplement.

Gluten sensitivity is a heterogeneous group of diseases (celiac disease, gluten intolerance and wheat allergy) that have different pathogenesis but similar symptoms (except for gluten allergy). All three conditions require a lifelong diet that excludes the consumption of gluten-containing products.

In the presence of permeable intestines, a gluten-free diet is always recommended, as in this case the consumption of gluten causes problems. If there are no permeable intestines, gluten is not harmful. 

Another common problem is lactose intolerance , which is a different condition from milk allergy. The clinical picture of lactose intolerance is manifested in bloating, wheezing and colic-like pain, flatulence, diarrhea, nausea and vomiting soon after consumption of milk and dairy products.

It should be distinguished from milk allergy , which debuts in early childhood and in addition to symptoms on the side of the gastrointestinal tract is manifested by rashes and swelling of the body, less often involves the respiratory organs due to bronchospasm and very rarely anaphylaxis.

Lactose intolerance may impair the absorption of other nutrients and minerals in connection with intestinal disorders.
It is necessary to eliminate from the menu and histamine liberators. The elimination of histamine-free diet consists in consciously avoiding foods and beverages rich in histamine and those that cause its release from the body's cells.

It is also necessary to limit foods high in other biogenic amines and to discontinue all histamine-releasing drugs.

Histamine liberators have the ability to cause the release of histamine hidden in the cells of the body. Glutamate, for example, increases histamine levels. Bulgarian yogurt, for example, is also a very good product if the body does not have a problem with the processing of histamine. Yogurt also contains other bacteria that have the ability to cause increased histamine levels. Such are, for example, organelles, klepsiela. The bacterium itself produces histamine in the body. Some biogenic amines also reduce the breakdown of histamine in the body. Inhibition of DAO enzyme activity leads to an undesirable increase in the level of histamine in the blood. Decreased DAO activity may be due to a history of gastrointestinal infection or pre-existing chronic intestinal disease.

Histamine intolerance should always be considered in vague and atypical allergy-like complaints. Unfortunately, many physicians are not familiar with modern advances in the study of histamine.

Many people with histamine intolerance and mat at the same time intolerance to other foods. Each of these diseases is due to changes in the intestinal mucosa.

If a child suffers from stomach problems or has allergies, it is very likely that the intestines are affected. The intestinal microflora is only one part of the puzzle. It is very easy to understand if a faecal test is performed, but it is important to examine the exact parameters.  
The key to any chronic problem is to find the root cause and take a personalized approach. However, this often involves changing habits, the daily rhythm of life, food.