Causes of atopic dermatitis: how to recognize trigger factors?

Causes of atopic dermatitis: how to recognize trigger factors?

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Atopic dermatitis is an inflammatory, pruritic, chronic recurrent skin disease with typical distribution and morphology.
Being aware of the factors involved in the pathogenesis of the disease is an important first step in the primary prevention of the disease.
The condition is the consequence of the action or co-action of several factors, the most important being the genetic predisposition and immunological factors.

Genetic predisposition to atopic dermatitis

Regarding genetic predisposition, in 60-80% of cases there is a family history of atopic dermatitis.
The presence of a genetic component is supported by studies showing that the risk of a child developing atopic dermatitis is increased if one or both parents have the condition. In addition, the risk for developing the disease if one or both parents have asthma or allergic rhinitis is higher than in the general population.

Immunological factors in atopic dermatitis

In patients with atopic dermatitis, a wide range of immunological and non-immunological abnormalities have been reported both at skin level and in serum. From the prenatal period, especially during the last trimester of pregnancy, the foetus is protected from external factors by the mother’s immune system and the peptides and antimicrobial proteins in the amniotic fluid; the foetus synthesises antimicrobial proteins in the epidermis (defensine and cathelicidines). After birth, the first colonisation of the newborn with bacteria from the mother’s flora takes place, and in the immediate postnatal period, breastfeeding helps form intestinal microbiosis with an antimicrobial and stimulating role in the development of the immune system in the gut. Any disturbance of this microbiosis can cause pathogen invasion at this level.

External factors in atopic dermatitis

The prevalence of allergic disorders has increased over the past decades. The cause of this rapid increase cannot be explained by changes in population genetics, which is why environmental factors are considered to be a possible explanation.
In Japan, Australia and some European countries, the number of atopic patients has doubled or tripled in the last 10–20 years. Some causes include:

  • air pollution, mostly through intense road traffic;
  • increasing the standard of hygiene, “hygiene hypothesis”, but also increasing the aggression on the skin with detergents and soaps. Excessive bathing of babies, use of inappropriate cosmetics with harsh ingredients. Excessive hygiene could be responsible, among other things, for the absence of intestinal physiological colonisation with enterococci and bifidobacteria, which stimulate Th1 lymphocytes and induce immunological tolerance through secreted antigens and endotoxins. Some authors claim that premature bifidobacterial supplementation can prevent atopic dermatitis in those who are genetically predisposed, and may reduce the severity of the disease in those with clinical manifestations;
  • accumulating more and more allergens at home through changes in the cohabitation (presence of mites, cats, dogs);
  • smoking among young mothers, which is on the rise;
  • chemical nutritional additives;
  • changing food behaviour by introducing new foods (especially exotic fruits, peanuts, etc.). Early diversification of diet seems to increase the frequency of atopic dermatitis;
  • less exposure to infections (measles virus, hepatitis A virus, helicobacter pylori, toxoplasma gondii, lactobacillus ruminus, etc.).
  • respiratory infections and dental eruption can trigger atopic dermatitis in babies and young children.
  • for all ages, stimuli susceptible to cause the hyper secretion of sweat (excitement, heat, exercise, occlusion with clothing or ointments) may lead to violent itching and a new spurt of atopic dermatitis. Contact with wool and lipid solvents aggravates atopic dermatitis. Sometimes menstruation and pregnancy have an unfavourable effect. Although some food allergens can trigger or exacerbate atopic dermatitis, an excessively restrictive diet can affect height and weight development in children.

Key elements to remember:

  • identifying the factors involved in atopic dermatitis is an important step in the primary prevention of this condition, certain factors, particularly environmental ones, can be influenced;
  • control of irritant factors (detergents, cosmetics soaps, chemicals, pollutants, abrasive materials, extreme temperatures and humidity);
  • emollients should be used after bathing;
  • avoiding smoking during and after pregnancy
  • avoiding and prompt treatment of over-infection.