Pediatric Dermatology

Characteristics of Children’s Skin

From the outside in, the skin is divided into the epidermis and the dermis, with subcutaneous fat and a muscle layer beneath them. The epidermis is further divided into four layers, the outermost of which is called the keratin layer (stratum corneum). The keratin layer is 0.01–0.03 mm thick in adults, and in children it is said to be one-third to one-half of that. Because the keratin layer protects the skin from external irritation, a child’s skin can be said to have a weaker barrier function.

The amount of sebum a child produces also varies greatly with age. In the newborn period, sebum production is brisk due to the influence of hormones from the mother, but production decreases from around three months of age, and from about age one to six sebum production is at its lowest of a lifetime. After that, from around puberty, sebum production begins to increase again. A baby’s skin tends to be oily at first and then dry.

In addition, because babies have short necks and plump folds of flesh, skin stays pressed against skin for long periods under the neck, at the armpits, at the base of the groin, and at the wrists and ankles, so sweat collects and the areas become prone to chafing.

Because of these characteristics, skin problems are common in children. In infancy there are also many diaper-related troubles, and once a child starts nursery or kindergarten the chances of catching various infections increase. A child may also have a congenital skin condition. Naturally it is the parents who provide care, but especially with a first child there is often a lot of uncertainty. Please come and consult us.

Skin Conditions Commonly Seen in Children

Infantile eczema

From a few weeks to a few months after birth, eczema and dermatitis develop easily and are collectively called infantile eczema, but their underlying nature varies. As noted above, in the newborn period sebum production is brisk, so the scalp and forehead in particular tend to become red and develop seborrheic dermatitis with yellow flakes.

After that, as sebum production decreases, some children develop asteatotic (dry skin) eczema. Overuse of soap makes the skin especially prone to dryness. Redness of the buttocks and the base of the groin caused by irritation from the diaper itself or from stool and urine is called diaper dermatitis.

All of these are treated with topical medication, but appropriate skincare is most important. Please also see our eczema and dermatitis page.

Treatment: appropriate skincare, moisturizing, topical steroids

Learn more about eczema and dermatitis

Impetigo contagiosa (tobihi)

A bacterial infection seen often in summer. It starts from a minor injury or a scratched patch of eczema, and the blisters and scabs spread by “flying” from one spot to another. It is often caused by group A beta-hemolytic streptococcus or Staphylococcus aureus; in the case of S. aureus, many blisters form because the bacteria produce an enzyme that detaches the skin.

It spreads easily among groups, but under the School Health and Safety Act it is classified as a Category 3 disease, for which the decision to keep a child home is made at the doctor’s discretion; usually the child can attend nursery as long as the affected area is covered with gauze or the like so that it does not touch other children. However, pool play cannot be protected against, so it is best avoided.

Treatment: oral and topical antibiotics

Molluscum contagiosum (water warts)

A viral infection common in children, in which numerous smooth, pink bumps a few millimeters in size appear in various places on the body. It is caused by a virus called the molluscum contagiosum virus, but a secondary bacterial infection can also occur, causing redness, swelling, and pus.

It sometimes resolves on its own over several months, but if the child is scratching them open we recommend treatment. Removing them by pinching with tweezers is common, but because it is painful, we sometimes apply an anesthetic tape and wait an hour before the procedure.

For children who do not do well with the procedure, we may treat with 3A M-BF Cream, which contains silver with antiviral action (“M-BF Cream,” self-pay (see the price list)).

When applied twice a day, if it is effective the affected area starts to turn red in about two weeks to two months, and then disappears over about a month. If it has not cleared after three months, it may be better to remove them by pinching.

Treatment: spontaneous healing, removal, topical cream

Aberrant Mongolian spots (blue birthmarks)

A Mongolian spot is a bluish birthmark present from birth on the buttocks or lower back, which most East Asian people have. When it occurs somewhere other than the buttocks or lower back, it is called an aberrant Mongolian spot. It looks bluish because the pigment-producing cells called melanocytes are located deep in the dermis.

Mongolian spots on the buttocks usually fade and disappear on their own at around four to ten years of age, but aberrant Mongolian spots often remain, so treatment is considered in view of their appearance.

Treatment is laser irradiation every three months. The ruby laser, YAG laser, and alexandrite laser are covered by insurance; our clinic is equipped with a laser device called the Discovery Pico Plus and can use the Q-switched ruby laser and the pico YAG laser.

However, insurance covers the Q-switched ruby laser for up to five sessions. Starting laser treatment early works better because the skin is thinner. But if the laser is too strong, side effects such as the color turning white or scarring can occur. Parents naturally want it cured quickly, but it goes better if you take a gradual, unhurried approach to lightening it. During laser treatment, we recommend applying sunscreen to prevent pigmentation.

Because the laser is painful, an anesthetic tape or cream may be used, but the amount that can be used is limited due to side effects, so a large area cannot be fully covered.

Treatment: laser (Q-switched ruby laser, pico YAG laser)

Café-au-lait macules (brown birthmarks)

A pale brown patch that can appear anywhere on the body.
It does not become raised, so on its own it can be left alone, but if its appearance bothers you, laser treatment is performed.

However, the results of laser treatment are not very good. Treatment under the age of one tends to clear well, but in adults it is said to work well in only about 20% of cases; in some people it recurs, or, far from working, it can even darken further due to post-inflammatory hyperpigmentation, a side effect of laser treatment.

Even if it darkens, it often fades over time, but that only returns it to how it was, and returning to that state can take from several months to more than a year. There is also a risk that the laser works too well, causing “whitening” where the area becomes lighter than the original skin color, or a mottled mix of lighter and darker areas that actually looks worse.

For a large area, to avoid the whole thing darkening or whitening, it is a good idea to do a test irradiation on just a part. Incidentally, it is said to respond better when the border is jagged, like a map.

The lasers used for café-au-lait macules include the ruby laser, the alexandrite laser, and the YAG laser. However, of these, only the Q-switched ruby laser is covered by insurance, for up to two sessions spaced three months apart.

Our clinic is equipped with a laser device called the Discovery Pico Plus and can use both the pico YAG laser and the Q-switched ruby laser. Using the pico YAG laser is a self-pay treatment.

As for pain, an anesthetic tape or cream may be used, but the amount that can be used is limited due to side effects, so a large area cannot be fully covered.

Treatment: laser (Q-switched ruby laser, pico YAG laser)

Capillary malformation / infantile hemangioma (strawberry hemangioma) (red birthmarks)

There are two kinds of red birthmarks commonly seen in newborns.

A capillary malformation (port-wine stain) is a red birthmark that is generally not raised and can appear anywhere on the body, but often forms between the eyebrows, on the eyelids, or on the back of the neck. In English-speaking countries, those on the face are nicknamed an “angel’s kiss” and those on the back of the neck a “stork bite.”

There are no problems other than appearance. Red birthmarks on the eyelids often disappear on their own by around age two, and because the eyelid is a difficult area to apply a laser, we often watch and wait. Those on the back of the neck are called an Unna nevus and often persist, so if it bothers you, laser treatment may be done.

However, because it becomes less noticeable once hair grows in, and because there is a risk of laser-induced hair loss, it is not always the case that laser is the better choice. The laser is a type called a pulsed dye laser, and our clinic uses the V Beam II. Note that when this red birthmark is seen over a wide area, it may be part of a vascular malformation syndrome, accompanied by abnormalities of other blood vessels in the body.

Treatment: laser (pulsed dye laser)

An infantile hemangioma (strawberry hemangioma) typically appears soon after birth as a small red spot and grows rapidly over a few months into a lump.

Because it is bright red with a bumpy surface, it was long called a “strawberry hemangioma,” but recently it is increasingly called an “infantile hemangioma.” (In addition to the “plaque type” and “tumor type” that form on the skin’s surface, there is also a “subcutaneous type” that appears bluish beneath the skin.) Even if left alone it naturally regresses, peaking at around age one, but it can leave slack skin, much like a belly after rapid weight loss, or a scar, so in recent years active treatment is recommended.

Also, in areas that affect function, such as near the eyes, nose, or mouth, early treatment is desirable even when the lesion is small. Treatment includes an oral medication called Hemangiol® syrup and laser treatment. When oral treatment is considered necessary, we refer you from our clinic to a specialized facility.

Depending on the hospital, some facilities require a one-week hospital stay when starting the medication, while others start it on an outpatient basis. The laser treatment is a pulsed dye laser, and our clinic uses the V Beam II. The oral medication and laser treatment are sometimes combined. Because the approach also changes with how fast it is growing, please bring any past photos that show the lesion.

Treatment: oral medication (Hemangiol® syrup), laser (pulsed dye laser)