Atopic dermatitis is a chronic, recurrent, inflammatory, pruritic dermatological disease whose pathogenesis involves both inflammatory factors and abnormal skin barrier function. It is currently believed that atopic dermatitis occurs in a significant genetic background. It is associated with the progress of industrialization, environmental factors, dietary factors, indoor and outdoor air pollution, fetal growth, and early infections. Atopic dermatitis usually develops before the age of 5 years, and may also develop in adults, but less frequently. Patients often feel extremely itchy skin, and after scratching, the affected skin becomes red, swollen, cracked, oozes clear fluid, and finally hardens and flakes. Some children get better or recover with age, but their skin remains dry and easily irritated, while others may still suffer from atopic dermatitis even after they grow up.
What is “atopic”?
The key to accurately grasp the definition and scope of atopic dermatitis and to distinguish atopic dermatitis from eczema and other skin diseases is the understanding of “atopic”. The term “atopic” means
(i) a familial predisposition to develop asthma, allergic rhinitis, or eczema.
(ii) Allergy to allergic proteins.
(iii) High serum IgE values.
④ an increase in eosinophils in the blood.
Typical atopic dermatitis must have ① – ④ at the same time and have eczema clinical manifestations.
The clinical classification of atopic dermatitis
1. Exogenous atopic dermatitis
Individual or family history of respiratory allergy (e.g. asthma, allergic rhinitis, chronic cough), elevated total IgE levels in the blood, and detectable atopic allergens. Seen in 70% of patients with atopic dermatitis.
2. Endogenous atopic dermatitis
The patient has no family history of respiratory allergy, and the total IgE level in the blood is normal. and no specific allergens can be detected. Early onset with dry dermatitis. Seen in 30% of patients with atopic dermatitis.
Three, atopic dermatitis triggering factors
1, the relationship with allergic reactions: respiratory allergic reactions are often associated with atopic dermatitis. The most common allergens are dust mites, pollen, animal dander and molds.
2, and food allergens relationship: mainly seen in infants and children suffering from moderate to severe atopic dermatitis. Milk, eggs, peanuts soybeans and wheat are the most common allergens. Consumption of eggs is often associated with exacerbation of atopic dermatitis. A tendency for reactions to peanuts, fish, nuts, and shellfish to persist.
3. Reactions to microorganisms: Microorganisms, especially Staphylococcus aureus, colonize more than 90% of atopic dermatitis lesions. Patients with atopic dermatitis are also prone to viral infections and superficial fungal infections.
IV. Clinical staging and signs of atopic dermatitis
Atopic dermatitis is divided into 3 clinical stages, namely infancy, childhood and adolescence or early adulthood, depending on age, site of onset and morphological changes in the lesions. These stages may cross over each other or may be separated by the self-healing of the disease at one stage.
Infantile stage (birth – 2 years): In the infantile stage, it occurs mostly in infants after 40 days of life, and a few may develop within the first month of life. The manifestations are acute and subacute eczema, with lesions on the scalp, face and extensor side of the limbs, and chapping, oozing and crusting at the eardrum; the diaper area is generally not involved; the affected child is consciously and intensely itchy. At about 18 months of age, the characteristic flexural (elbow and popliteal fossa) involvement begins to appear and mossy changes occur. By 2 years of age, about 80% of infants with atopic dermatitis will be largely cured, with the remainder entering childhood.
Childhood (3 – 11 years): Childhood atopic dermatitis can be a continuation of the infantile period or a new onset in childhood. It is characterized by a mossy appearance and presents as an eczematous and itchy rash. The flexural involvement is more pronounced and can spread to the neck, wrist flexure and inguinal area, and in those with generalized lesions the extensor calf, hands, perioral and periocular areas can also be involved. It is called ‘four curved wind’ in Chinese medicine.
Adolescence or early adulthood (12 – 20 years old): lesions tend to occur on the face, neck, flexors and upper trunk, and the main symptoms are pruritus, mossy changes, itchy rash, scratches and crusting, with dry skin and mossy changes remaining the most prominent features. There is often a typical central pale area on the face. Most patients have spontaneous regression of the lesions after the age of 20 years; a few severe cases may persist into old age.
Signs that aid in the diagnosis of atopic dermatitis
Atopic dermatitis can be accompanied by a series of characteristic skin changes, including dry skin, auricular fissures, ichthyosis, palmaris, follicular keratosis, infraorbital folds, orbital capsule dark halo, peri-hair elevation, nonspecific hand and foot dermatitis, white furunculosis, anterior cervical folds, papillary eczema, recurrent conjunctivitis, and white scratchy sign.
VI. Differences and links between atopic dermatitis and eczema
Although the current textbooks and reference books treat atopic dermatitis and eczema separately, the general international academic view is that there is no eczema of unknown origin, eczema is only a temporary diagnostic term, and as research progresses, the eczema that has found its cause is diagnosed as the corresponding dermatitis
The early presentation of atopic dermatitis is very similar to that of common eczema in infants. If a pinhead-sized red papule appears on the face, there will also be symmetrical erythema and scaling, and in severe cases, redness, small blisters, vesicles and oozing, often accompanied by very pronounced itching, but the two still have their own characteristics.
1, atopic dermatitis compared to ordinary eczema, generally heavier symptoms. The latter’s rash is more limited and only occurs in a part of the child’s body, such as the cheeks, back of the hand, etc.; while the former’s rash is more extensive, often affecting the child’s scalp, ear, and in severe cases the trunk, limbs, including the back of the hands and feet can be involved, and with age, the typical hypertrophic, moss-like rash gradually appears in the neck, elbow fossa, popliteal fossa.
2, atopic dermatitis is more likely to recur compared to ordinary eczema. The condition of children with atopic dermatitis is sometimes mild and sometimes severe, and the duration of the disease often lasts > 3 months.
The skin of children with atopic dermatitis can be abnormally dry and rough, and 60% – 70% of children have a family history of asthma, allergic rhinitis, or atopic dermatitis.
4. Children with atopic dermatitis may have pale face, dark circles under the eyes, ichthyosis, diffuse dandruff, lip inflammation, etc.
Many of the current eczemas such as ear eczema, breast eczema and hand eczema are among the manifestations of atopic dermatitis at different times and in different places.