Atopic dermatitis

Atopic dermatitis or atopic eczema is a dermatitis (skin inflammation) typically associated with severe pruritus (itching) and can be related to other allergic diseases such as asthma and allergic rhinitis.

It is usually difficult to treat and, therefore, greatly affects the quality of life of the individual and their family and may represent a significant economic burden.

It is a disease that has been increasing worldwide, apparently due to its relationship with the Western lifestyle, particularly with diet, excessive antibiotic use, smoking, absence of breastfeeding, and increased environmental pollution.

The characteristic symptoms of atopic eczema are:

• Intense itching of skin areas, mainly flexures of the extremities. The intense itching initiates the sequence of spontaneous lesions or those secondary to scratching, which leads to eczema formation.
• Dry skin with scaling.
• Eczema lesions with erythema, scaling, vesicles, exudation, fissures, scratch lesions, and thickened areas (lichenification).

In patients with atopic eczema, there is a decreased immunity against certain skin infections. Therefore, eczema often becomes infected and chronically inflamed secondarily.

Additionally, atopic dermatitis is associated with other typical signs and symptoms of atopy that also occur in people with allergic rhinitis and asthma, such as:

• Dry skin or xerosis.
• Rough skin or "sandpaper" skin.
• Pallor in the center of the face and darkening around the eyes (dark circles).
• Scaling around the mouth.

Furthermore, atopic dermatitis presents in different forms and distribution depending on the patient's age.

• In infants, before the first year of age, eczema lesions usually appear on the head (cradle cap), on the face sparing the eyes, nose, and mouth, or spread over the skin of the entire body. In this form of presentation, it is usually a very striking and intense condition, but its prognosis is very good, disappearing before age 5. Pruritus (itching) may cause difficulties sleeping.
• In school-age children, eczema lesions predominate in the flexures of extremities, on the neck, and in the area behind the ears, sometimes with eczema lesions on the lips and eyelids.
• In adults, there are two forms: one is due to persistence of childhood eczema with predominantly flexural lesions, and another that appears in adulthood with disseminated lesions, frequently erythrodermic with significant involvement of the face and neck that tends to become chronic. Nipple eczema is common in adolescent girls, and pigmentation alterations (paler or darker areas) may remain on the skin when the original lesions disappear.
• There are other minor forms of atopic eczema:
  • Pityriasis alba: These are whitish lesions on the skin with scales and dry skin that may appear on the face or distributed throughout the body.
  • Atopic cheilitis: These are eczema lesions on the lips with fissuring.
  • Atopic pulpitis: This appears with scaling and fissuring of the fingertips and toes.

Several factors have been associated with the onset of atopic dermatitis:

• Heredity: occurs more frequently in people with a family history of atopic dermatitis and other allergic diseases (rhinitis, asthma, conjunctivitis, or eczema).
• Other concomitant allergic diseases: allergic rhinitis, asthma, conjunctivitis, and food and dust allergies.
• Increased Immunoglobulin E or IgE, which is an antibody that becomes elevated in the blood of people who suffer from certain allergies. This elevated IgE typically binds to inflammatory cells (mast cells and basophils) and, when exposed to specific stimuli (foods, mites, pollens, etc.) or nonspecific stimuli (stress, temperature changes, humidity, skin irritants), causes the release of histamine accumulated inside these cells, producing itching.
• Apparently, excessive or inappropriate use of antibiotics can alter the microbiota (beneficial bacteria for the body) and promote atopy in general.

Once characterized as atopic eczema based on family history of allergy and the characteristic distribution and symptoms of this eczema, the goal is to identify the underlying allergic causes that trigger histamine release.

Since the cause of histamine release is the binding of IgE to various allergens, an allergy study should be performed to determine the causes.

In most cases, elevated total circulating IgE levels are observed in blood.

From this point, the possible specific allergy to foods (egg, milk, fish, fruits, vegetables, nuts, etc.), dust mites, and pollens should be determined using specific IgE testing techniques (CAP, RAST, etc.).

Additionally, skin allergy tests can be performed using prick tests, or even patch tests.

The objective is to identify specific allergic factors that cause itching in order to exclude them from the patient's environment. For this purpose, it is sometimes necessary to verify the cause-effect relationship through exclusion-addition diets, checking for improvement and worsening when eliminating or adding suspected foods.