How to recognize eczema?

L’eczema is an itchy dermatosis  characterized by non-contagious inflammation of the skin which is accompanied by redness, fine blisters, scales and itching. It can start very early in life, and is seen even in infants. People with this condition experience periods commonly called “eczema flares”, during which symptoms worsen. These attacks, of varying duration, are interspersed with periods of remission. Eczema is often associated with asthma or various allergic reactions.

The mechanism ofeczema is not yet well understood, it would affect both the immune system and the skin cells that act as a barrier for allergens. Eczema is said to be a genetic disorder, but environmental factors such as the presence ofchemical irritants or stress influence its appearance.

Among all the maladies de la peau, eczema is the most frequent: this disease motivates up to 30% of dermatology consultations. In industrialized countries, it would reach 15% to 30% of children and 2% to 10% of adults². Recent estimates suggest that eczema cases have doubled and perhaps even tripled over the past 30 years.

To explain this increasing incidence of eczema, various hypotheses have been put forward. For example, it is suspected that the change in infant feeding habits caused by the abandonment of thefeeding and early exposure to food allergens would play a role in the onset of this disease at a young age. Indeed, it seems that exclusive breastfeeding of the infant during the first 3 months protects in part against dermatitis atopic³. On the other hand, there would be no link between the early introduction of solid foods and the appearance of eczema in young children.⁴.

Main types of eczema

There are several types ofeczema, although the term “eczema” is usually used to refer to the different variants of the disease.

Atopic eczema or atopic dermatitis

It is the most common form of chronic eczema. Atopy is the tendency to react with allergic reactions mediated by antibodies called IgE in contact with allergens that are normally harmless to the rest of the population (dust, pollen, animal hair, etc.). People with atopia often have various allergic reactions, either simultaneously or alternately, such as hay fever, hives, asthma or food allergies. These allergies often have a hereditary component since they are observed in many cases within families where at least 1 of the members suffers from it.

Atopic dermatitis affects 10 to 20% of children and 2 to 3% of adults in Europe. The disease begins most often in infants and most often persists in childhood up to 5-6 years, but it sometimes lasts into adulthood in about 15% of patients.

Here is what we know about the causes of atopic dermatitis which is a multifactorial disease involving genetic and environmental factors:

Atopic dermatitis is a disease with a genetic factor since 50 to 70% of parents of atopic children have a sign of atopy (eczema in childhood for example) and 70% of identical twins both have atopic eczema . This genetic factor is polygenic because it affects at least 2 types of genes:

• superficial skin barrier genes: the skin has a very fine and very resistant superficial barrier, but patients with atopic dermatitis carry genetic mutations, in particular in the gene encoding filaggrin, a structural protein of the epidermis playing a role in the structure of the skin barrier and maintaining an optimal level of skin hydration. As the skin plays its barrier role less, antigens and chemical irritants can more easily penetrate it.
• genes of the cutaneous immune system: thus atopics react more to their environment, and trigger inflammatory skin reactions in the presence of antigens, notably involving Langherans cells (antigen presenting cells), lymphocytes (white blood cells producing antibody)…

Atopic dermatitis is a disease in which environmental factors are involved and in particular:

• The digestive flora: we have been discovering in recent years to what extent the microbiota, or composition of the digestive bacterial flora, plays a role in many diseases and in the individual response to treatments. Atopic dermatitis is not lacking in this rule since it has been discovered that the microbiota is a complex ecosystem that intervenes in the maturation of the immune system. Anomalies of early diversification of the intestinal microbiota have been observed in children at risk of atopia as well as in newborns at risk of atopy.
• Skin flora: the newborn’s skin microbiome is gradually formed after birth from the mother’s microbiome and the environment. As with the intestinal microbiota, there are differences between the skin microbiome of atopic children and that of non-atopic children, especially when there are outbreaks of atopic dermatitis, during which there is a proliferation of strains of staphylococcus (Staphylococcus aureus in 90% of cases). cases and staphylococcus epidermidis), in connection with a deficit in cutaneous immunity through a deficit in “natural antibiotics” in the skin: beta defensins.

Thus, local treatments for atopic dermatitis tend to promote natural bacterial diversity on the surface of the skin to limit the place of Staphylococcus Doré. Thus, antiseptics should be avoided in atopic dermatitis and the local corticosteroid therapy so dreaded by mothers tends to promote bacterial diversity, to the detriment of Staphylococcus Doré.

The increase in the frequency of atopic dermatitis has been regular for several decades in developing countries, which suggests that environmental factors play a major role in the pathophysiology of the disease and in particular the reduction in exposure. infectious agents in early childhood: recent studies confirm that the “urban Western” lifestyle exposes an increased risk of atopic diseases compared to the “rural” lifestyle (exposure to bacteria and parasites from early childhood), in particular in genetically predisposed populations and in the same geographical areas. This therefore also evokes other factors more present in the “urban Western” way of life (role of giving up breastfeeding? Milk allergy? Greater concentration of polluting substances and allergens in the environment? )., but this remains to be scientifically proven. Finally, it should be noted that there is more eczema of the child in the countries of the North of Europe than in the countries of the South of Europe: one can thus wonder if there are not factors that can lead to childhood eczema in

northern countries (is the meticulous hygiene of young children in northern countries responsible for the increase in childhood eczema in these countries? are children in northern countries more subject to allergens than in the South? can the colder climate explain the greater frequency of childhood eczema in the countries of the North?)

All of these data made it possible to develop a “theory of biodiversity” protecting atopic dermatitis, which combines environmental biodiversity and the biodiversity of the various skin and digestive microbiomes.

How does atopic dermatitis manifest itself?

• In infants, lesions begin on the cheeks or even the forehead and scalp, then they extend to the extension faces of the arms and legs and the trunk. These are dry and rough or oozing and crusty rednesses. , which always itch (the infant tends to put his hands on it, which can cause scratches.
• After 2 years, atopic dermatitis lesions will predominate in the flexion folds of the elbows and knees or even the wrists.
• In adolescents and adults, the lesions are mainly localized on the face and neck (the Anglo-Saxons speak of “head and neck dermatitis”) and the limbs. They are often thickened (we speak of lichenification of the skin).

Complications of atopic dermatitis

– Superinfection by Staphylococcus aureus or “impetiginization”, responsible for a purulent discharge, sometimes bubbles and yellow crusts like honey.

– Superinfection by the herpes virus (HSV-1 especially). It is rare (5% of children with atopic deratitis) but formidable, it results in a sudden worsening of the disease and the appearance of small multiple vesicular lesions reminiscent of chickenpox, giving wounds. We speak of Kaposi-Juliusberg syndrome.

The management of atopic dermatitis in children therefore resorts to limiting the contributing factors and in particular the elements accentuating skin dryness by applying moisturizing creams, avoiding too hot and prolonged baths and using mild soaps (from bath oil type or surgras for example). Hydrotherapy is one of the therapeutic weapons making it possible to fight against atopic eczema, but it is generally only used in conjunction with conventional treatments based on cortisone creams, particularly during relapses.

Contact dermatitis

Allergic contact dermatitis is characterized by eczema lesions appearing on average 3 days after skin contact with certain substances called allergens (this period can be extended to 10 days if it is the first contact of the skin with the skin). ‘allergen). This is an allergic reaction to the substance. This allergic reaction does not necessarily occur on first contact and it can appear after several months or years of tolerance to the allergen (one becomes allergic to a substance that one tolerates, for example, nickel in jewelry or coins. ).

Evolution

According to type of eczema, symptoms may last 1 or 2 weeks, or last for several years.

Complications

When scratched, the plaques ooze and become more irritated. Sometimes these areas can become infected. In particular, it is possible to contract ;

• impetiginization, which is a bacterial superinfection, in particular with Staphylococcus Aureus, eczema, characterized by the appearance of melicera crusts (like crystallized honey),
• cellulite. This complication is characterized by the sudden appearance of swelling on the skin of a limb, which becomes tender, red and hot.

In these cases, it is important to consult quickly.