Infants have an immature skin barrier function that weakens their skin defense against exogenous irritants [3]. In general, excessive use of body soap and shampoo for infants removes sebum from their skin, which induces dry skin and causes increased skin inflammation. In addition, drooling and finger sucking may stimulate the perioral skin and promote a barrier disruption. Although the age at AD onset varies in infancy, the majority of infants with AD naturally go into remission several months or years after onset.

A seasonal variation of AD symptoms may be observed, in which patients deteriorate during the winter and improve in the summer. In some severe cases, patients are unlikely to improve naturally, although they may live without any problems for 2–3 years after onset. Young infants show a drying of skin areas that are exposed to the outside air, such as the cheeks, forehead, and scalp, followed by skin flushing in the same region (Fig. 16.1a). As the disease activity of AD becomes stronger, the flushing becomes much worse. Itching occurs as papules appear. Scratch-injured papules become exudative and form a crust. Skin eczema can then spread across the entire face, including around the ears, perioral, cheeks, and chin (Fig. 16.1b).

In addition to the face, the neck is also susceptible to irritation by bacterial toxins. Flexure parts, including the axillar, cubital, and popliteal fossa, are susceptible to chemical irritants such as sweat and soap. Such stimuli may induce flashing, papules, and exudation in these skin areas. Vulnerable areas including the wrist and dorsum of the hands and ankle are affected by dryness. Furthermore, eczema spreads to extensor surfaces of the extremities in season when extremities are exposed (Fig. 16.1c). In general, the trunk and diaper area are usually spared, but when disease activity is strong, a disseminated erythema appears on the chest, abdomen, back, and waist (Fig. 16.1d), and the erythema then spreads over the entire surface of the trunk (Fig. 16.2c).

As children grow from infancy to school age, their skin tends to become gradually drier due to reduced sebum secretion ability. Their scope of activities also expands from home to school. Therefore, their skin can be exposed to a variety of irritants, such as sweat, sand, and mud on playgrounds, as well as chlorine in swimming pools, leading to deterioration in AD symptoms.

Skin symptoms may improve as children go through school, and unlike infancy, severe cases are relatively rare. Eczema on the face improves, while skin eruptions typically appear in the flexure portions including the neck, axillar cubital and popliteal fossa, inguinal, wrists, and ankles.

On the contrary, some patients complain of itching on the trunk and extremities, but their skin eruptions are unremarkable. As symptoms progress, the skin becomes dry with peeling scales and further severe excoriation (Fig. 16.2a, b). In rare severe cases, eczema spreads to the face and extremities. Erosions and blood crusts may often appear due to a repeated scratching. In addition, excessive scratching sometimes causes lichenification and prurigo nodules on the elbows, knees, and extremities (Fig. 16.2d).

Physical and mental growth and the lifestyle change greatly affect the clinical symptoms of AD. Particularly, stress, overwork, and anxiety associated with study and entrance exams increase. Such psychogenic factors can exacerbate AD symptoms and lead to repeated itching. In addition, social activities provide fewer opportunities to visit a medical institution, resulting in limited treatment.

After puberty, sebum secretion from the skin is increased due to sex hormones, and seborrhea and acne vulgaris are likely to occur. Skin eruptions overlap, especially on the face. During this period, eczema can extend from the neck to the upper chest region and the upper part of the back, spreading in the shape of a clothes hanger. The skin rash on the face increases again and the whole face turns red in more severe cases with AD (termed “red-faced”). Together with rashes on the face and the neck, it is distributed like a sculptural portrait (termed “portrait type”).

As the secondary changes based on long-term treatment appear, the skin manifestation in puberty is much more complicated compared to that in school-age children and infants. A red/purple pigmentation, prurigo, nodules, and skin atrophy influenced by steroid ointments may sometimes be observed. In some severe cases, the skin rash and resulting erythroderma may spread over the whole body.

Infants with an immature skin barrier function may be strongly affected by cold and dry air, especially on the scalp, forehead, and cheeks. The entire face (except the scalp) is highly affected by exposure to dust and other allergens and immunoglobulin E allergic reactions. Also, the use of body soap and shampoo greatly impacts the scalp, hairline, and around the ears. The eyelids and eyelid margins are influenced by allergic conjunctivitis as well as lacrimation. The perioral, cheeks, and lips may be impacted by drool and contact stimuli with food. The nasolabial region is influenced by blowing the nose due to allergic rhinitis.