Atopic dermatitis is a chronic, dry skin condition that occurs due to genetic and environmental factors. The goal of treatment is to reduce symptoms, maintain skin integrity, and improve quality of life.
What is Atopic Dermatitis?
Atopic dermatitis, more commonly known as eczema, is a chronic, dry skin condition seen in infants, children, and adults. In a typical pediatric scenario, parents schedule a doctor visit because their child has an irritated, itchy rash that fails to improve despite at-home treatment measures. Upon examination, the child’s skin has a rough, sandpaper-like texture, and there are areas of redness with evidence of scratching. Throughout the visit, the child repeatedly scratches the skin, sometimes to the point of bleeding. This cycle of itching, scratching, and worsening irritation is what classifies atopic dermatitis as one of the most frustrating skin conditions, both for children and their parents.
There are some aspects of atopic dermatitis that mimic other skin problems. Contact dermatitis may have a similar dry, irritated appearance. It differs, however, because it can be attributed to a specific cause. For example, a rash that develops after wearing a piece of jewelry is due to skin contact with the metal. Infantile seborrhea is often confused with atopic dermatitis, particularly when it affects the forehead. This type of rash may be seen as young as two weeks old, and it most commonly affects the scalp, forehead, and diaper area. Itching is less common, and the skin has an oily rather than a dry appearance.
Who Gets Atopic Dermatitis?
Cases of atopic dermatitis continue to increase among those in developed nations. The incidence in infants and children is approximately 20 percent. Genetics plays a role, and a family history of eczema, allergies, or asthma is common. Most childhood develop symptoms prior to the age of five, with initial signs detected as young as three months old. Whether or not symptoms persist or resolve can vary. Some infants “outgrow” their eczema by age two, while others experience flares until the teen years. In 70 to 90 percent of cases, however, atopic dermatitis resolves before adulthood.
What Causes Atopic Dermatitis?
Atopic dermatitis is influenced by both genetic and epigenetic factors. The primary reason it occurs is because of an ineffective skin barrier mechanism. The skin consists of three layers: the outer epidermis with keratin and pigment, a middle dermis with oil and sweat glands, and an inner subcutaneous fat layer. A fully functioning epidermis acts a waterproof barrier that retains skin moisture, and repels the sun’s UV-B radiation. A protein called filaggrin is one of the “building blocks” of keratin which provides strength and integrity to the epidermis. If a genetic mutation occurs, a defective version of filaggrin forms. This results in skin that easily loses moisture, and that is prone to irritation. 10 percent of the northern European population and up to six percent of Asians have this mutation. A few variants of mutated filaggrin have been noted among African Americans, but the overall prevalence is unknown. Additional mutations of skin structural components have been observed which can increase the severity of this disease.
Over the past few decades, a “hygiene hypothesis” has been proposed to explain why atopic dermatitis occurs. It is common for infants and toddlers to repeatedly put their fingers into their mouths. The gut microbiome develops as they touch objects, and then ingest whatever microbes are present. This stimulates the growth of bacterial flora within the gastrointestinal tract, and potentially protects against future atopy. Maintaining a living environment that is “too clean” can prevent this from occurring.
Atopic skin has a different balance of normal flora than healthy skin. Millions of bacteria, fungi, and viruses live on the skin and play an important role in its immune functions. If exposed to a pathogen, normal skin flora protects against the development of an infection. This becomes more difficult in the presence of atopic dermatitis. Because the mutated filaggrin protein creates an abnormal epidermis, it is easier for harmful organisms attach to the skin. These pathogens then multiply, and may colonize the skin surface. As a result, the skin microbiome becomes overwhelmed, and cannot suppress infections. Staphylococcus aureus, for example, commonly infects eczematous skin.
Flares of atopic dermatitis tend to occur during the colder months of the year. The skin becomes dry due to in-home heat and cold outdoor air. This is the case for the majority of infants and children with eczema. A smaller percentage, however, experience worsening of their symptoms in warm, humid environments.
Certain skin exposures can contribute to atopic dermatitis. Harsh soaps and detergents often irritate the skin, and impair its protective function. Recent studies have indicated a link between tobacco smoke exposure and eczema. Increased white blood cells, fibrinogen, and other inflammatory mediators at the subcutaneous level are felt to increase the skin’s permeability, therefore limiting its barrier function.
The classic signs and symptoms of atopic dermatitis are skin dryness with itching, redness, and irritation of the affected areas. Recent studies indicate that pain is also a common symptom due to the severity of skin irritation. Persistent scratching worsens the condition of the skin, and is associated with poor sleep quality in children. Areas with repeated flares may develop a scaly appearance as well as pigmentary changes. Different areas of the body are affected depending on the age of the child. The face, trunk, and extensor surfaces of the arms and legs are common locations for infants with atopic dermatitis. They often “squirm” or rub against surfaces to scratch and relieve the itching. In contrast, children and teens acquire lesions in the folds of the elbows, behind the knees, and in the creases of the wrists and ankles. Facial eczema may persist in older children, particularly on the lower eyelids. Skin areas that are free of atopic lesions typically remain dry and prone to pruritus.
Dyshydrotic eczema differs from classic atopic dermatitis. This type specifically affects areas of excessive sweating such as the hands and feet. Despite the increased moisture, the palms and soles become dry and itchy. The skin in these areas may blister and peel, exposing a raw and irritated inner skin layer.
The “Atopic March”
This concept refers to the progression of allergy-related symptoms that begin during infancy, and progress throughout the childhood years. The “march” begins with atopic dermatitis, and is followed by the development of asthma and allergic rhinitis. For example, a four month old with eczema may experience an allergic reaction when a new food is introduced months later. By the age of two, he or she may develop sneezing and watery eyes during the spring or summer. Although no direct causal relationship has been identified between eczema and allergies, some studies suggest that inadvertent skin exposure may be a trigger because of permeability of the epidermis.
The link between atopic dermatitis and asthma is felt to be the result of different genetic mutation than the filaggrin one. 60% of children with severe atopic dermatitis later develop asthma. Hereditary and environmental factors contribute to atopy, but it is also triggered by immune responses. The antibody IgE is a key mediator of allergic reactions. This antibody differs from those that fight infections. In addition to IgE activity, cytokines released by specific components of the blood called T Helper cells promote itching and inflammation.
The impaired epidermis of atopic skin is prone to bacterial infections because it is easier for bacteria to adhere to the skin. Staphylococcal and streptococcal infections are the most common types, and scratching often spreads the bacteria to other locations of the body. Such infections present as pus-filled blisters or yellow-crusted lesions. In these cases, antibiotics are a necessary component of the treatment regimen until the infection clears. Occasionally, a herpetic viral infection develops within the eczematous area of skin. Pain is the primary symptom, and clear fluid-filled blisters appear. Eczema herpeticum can be very serious if located near the eyes or the ears. It may self-resolve within two to six weeks, but anti-viral medication is typically prescribed. Note: in the absence of an infection, atopic dermatitis is NOT contagious.
Poor sleep quality is one of the most frustrating aspects of atopic dermatitis. The persistent itching makes sleep onset difficult, and it can cause frequent waking. Sweating during sleep can intensify the itching. Further complicating the situation, the sleep hormone melatonin may be suppressed because of the sleep disruptions. Daytime sleepiness can affect school performance or mimic attention deficit disorders. There has been discussion of growth stunting in children with atopic dermatitis due to interrupted sleep, but results have been inconsistent, and further research is necessary.
Atopic dermatitis can have psychosocial effects. Depending on the severity and location, the appearance of atopic skin can be upsetting for both parents and their children. Some children may attempt to hide their eczema with clothing, or avoid situations where their skin is exposed. They may avoid wearing a swimsuit or changing in a school locker room due to embarrassment. Parents are often concerned about skin pigment changes in the affected areas. Trying multiple remedies and treatments with limited success is also stressful.
– Supportive Care –
Preventative skin care is the first line of treatment for atopic dermatitis. A diligent regimen can reduce the need for medications. The daily application of emollients prevents flares, and replaces skin moisture losses. There are many available options, but a product that works well for one child may be ineffective for others. Using these emollients several times a day, along with the application of wet wraps at bedtime, can facilitate healing in stubborn areas. While bathing is important to keep the skin clean and to reduce infections, if done too frequently, it may exacerbate eczema. Infants and younger children usually do well with a bath every two to three days. Care should be taken to avoid very hot water which can irritate dry skin. Fragrance-free, dye-free soaps or body washes are gentler on eczema prone skin. Such “sensitive skin” products should also be used for laundering clothing, towels, and bedding.
– Topical Medications –
Topical steroid creams have been the mainstay of eczema treatment for years. When used appropriately, they provide significant relief of symptoms, and reduce inflammation of the skin. They are the first-line medications in most situations, and efforts should be made to address parental concerns about their safety. There are low, medium, and high potency options. A once-a-day application is typically recommended, although twice-a-day dosing is often used in clinical practice. Lower potency versions are typically prescribed for a limited number of weeks due to the potential for longterm side effects (I.e. thinning of the skin, stretch marks). Stronger topical steroids are reserved for severe flares, and are used for a shorter duration. With these, some skin absorption occurs, and there is the potential for systemic side effects if larger skin areas are treated. In addition, these medications are not recommended for use on the face or genital areas.
Another class of medication for atopic dermatitis became available in the early 2000s: calcineurin inhibitor creams. Calcineurin is important to T Helper cell function. These creams, therefore, reduce the ability of T Helper cells to cause the kind of inflammation seen in atopic dermatitis. Two versions are available, and they are approved for children over the age of two. They are safe for daily use and on sensitive areas of the body. A competitor non-steroidal product was approved in 2016: a phosphodiesterase-4 inhibitor ointment. While the exact anti-inflammatory mode of action is unknown, this medication reduces the troublesome itching, and promotes skin healing. It is recommended for ages three months and up.
– Oral Medications –
For severe cases, an allergist or dermatologist may rarely prescribe a short course of oral steroids. The reasoning behind this is to get control of the most severe lesions so that topical treatment will be more effective. This treatment option is considered only when absolutely necessary because of systemic immunosuppression, and the effects on growth parameters. Previously used oral immunosuppressants such as methotrexate and cyclosporine are no longer the mainstay of oral eczema therapy.
– Infection Control –
In scenarios where a skin infection develops, antibiotic creams are prescribed. Most infections respond well to topical versions, and oral antibiotics are rarely necessary. When these infections occur frequently, bleach baths may be recommended as a preventative measure. This involves adding 1/4 cup of regular household bleach to a full bathtub of water (a reduced amount for smaller infant tubs). The diluted bleach reduces the colonization of staphylococcus and streptococcus on the skin surface, thus lowering the possibility of subsequent infections.
– Itch Control –
At times, despite the best skin care regimen, the itching of atopic dermatitis significantly affects the quality of life. In such cases, oral antihistamines can be effective, especially when given at bedtime. They not only reduces the itching, but their sedative effects improve sleep quality.
– Biologics –
Injectable immunomodulators have been studied over the past few years, and are effective in reducing the symptoms of atopic dermatitis. Omalizumab reduces IgE activity, and is helpful in treating both eczema and asthma symptoms. The newest option is dupilumab. It blocks the inflammatory cell mediators that trigger an increase in IgE antibodies. It also lowers the activity of cells that cause allergic reactions (T Helper, eosinophils, basophils, mast cells). Unlike oral steroids, the immune system is not suppressed. Dupilumab is approved for children six and up, and it is dosed every two or four weeks. Many new biologics are under development, and may revolutionize the way atopic dermatitis is treated in the future.
– Prevention Measures –
A diligent skin care regimen is the best way to protect eczema-prone skin. Daily use of emollients reduces the dryness that leads to exacerbations. Efficacy, however, can vary with the level of compliance and consistency. The use of emollients during the neonatal period, however, has not been shown to prevent the future development of atopic dermatitis.
Many research studies are evaluating other prevention strategies. One study concluded that their cohort of at-risk infants and children had fewer diagnoses of atopic dermatitis when soap was strictly avoided from birth. Other studies are evaluating the maternal ingestion of prebiotics or probiotics during pregnancy. Theoretically, a protective gut microbiome may develop in the growing fetus, thus reducing the likelihood of atopic dermatitis later in life. Vitamin D is an immunomodulator, and plays role in filaggrin and keratin formation. There is ongoing research to determine whether or not vitamin D supplementation can prevent eczema flares, especially during the winter months. Although therapeutic for non-breastfed infants who have a cow’s milk protein allergy, partially hydrolyzed infant formulas are not a recommended preventative measure for atopic dermatitis.
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