Atopic Dermatitis (Eczema)
Atopic dermatitis (AD), also known as eczema, is a chronic condition of the skin that affects an estimated 9 to 30 percent of people in the United States.
Video: An NIAID research team has found that wet wrap therapy combined with education on long-term skin care can dramatically improve the lives of children with severe eczema.
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Symptoms and Causes
The symptoms of AD include dry, itchy skin that can become swollen and cracked and can weep clear fluid when scratched. People with AD experience cycles of worsening symptoms followed by periods of improvement. They also have an increased susceptibility to certain skin infections.Although the specific causes of AD are unknown, it is thought to occur from a combination of genetic, immunologic, and environmental factors.
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Related Conditions and Complications
AD is closely associated with other allergic diseases, including food allergy, asthma, and allergic rhinitis (hay fever). Children whose parents have asthma and allergies are more likely to develop AD than children of parents without allergic diseases. Approximately 30 percent of children with AD have food allergies, and many develop asthma or respiratory allergies. People who live in cities or drier climates also appear more likely to develop AD.Bacterial Infections
A major health risk associated with AD is skin colonization or infection by bacteria such as Staphylococcus aureus. Sixty to 90 percent of individuals with AD are likely to have some staph bacteria on their skin and many eventually develop infection, which worsens the AD. Antibiotic-resistant strains of S. aureus, notably methicillin-resistant S. aureus (MRSA),are a significant public health concern, especially for patients with AD.
Viral Infections
People with AD are highly vulnerable to viral infections of the skin. When people with AD are infected with herpes simplex virus, a subset of this population develops a severe and widely disseminated skin infection called atopic dermatitis with eczema herpeticum (ADEH).
People with AD should not receive the smallpox vaccine, even if their AD is in remission, because they are at risk for developing a severe and widely disseminated infection called eczema vaccinatum (EV). EV is caused when the live attenuated vaccinia virus in the vaccine reproduces and spreads throughout the body.
People who live with a person with AD or a history of AD should not receive the smallpox vaccine because of the risk that they will transmit the vaccinia virus. For this reason, between 11 and 34 percent of the population of the United States may be ineligible for smallpox vaccination.
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Research
NIAID established the Atopic Dermatitis and Vaccinia Network (ADVN) in 2004 to better understand why some people with AD are at a high risk for EV. The ADVN was renewed as the Atopic Dermatitis Research Network (ADRN) in 2010, with expanded goals to understand immune system responses to viral and bacterial skin infections in healthy individuals and in people with AD.ADRN examines the following:
- Defense mechanisms of the skin, both immune defenses and skin barrier function
- Genetic variants that contribute to the development and severity of AD and the relationship of these variants to infections
- Susceptibility to colonization and infection by bacteria including S. aureus and MRSA
- Susceptibility to infection by viruses, including herpes simplex virus and vaccinia virus
- Vaccine responses among individuals with AD
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Accomplishments
NIAID-funded investigators have taken important first steps toward understanding differences in the ability of the skin to protect against infections in people with and without AD. Their research has shown the following:- Immunization with modified vaccinia virus Ankara, a candidate smallpox vaccine, is effective in protecting mice with AD from the development of EV.
- When compared with the skin of healthy people, the skin of people with AD has lower levels of antimicrobial peptides, which protect against infection, and individuals with ADEH have even lower levels.
- People with AD have high levels of the key allergic disease antibody, immunoglobulin E (IgE), and high levels of specific IgE antibodies against many inhaled and food allergens.
- There is a close relationship between AD and skin barrier defects, and people with ADEH have even higher levels than people with AD without EH.
- People with ADEH may be more susceptible to certain skin infections than people with AD.
Major Projects
ADRN investigators are working on several projects that include the following:- A comparison of responses to herpes simplex virus in healthy people, patients with AD, and subsets of patients with AD to identify factors that may increase susceptibility to infection.
- A comparison of responses to S. aureus and MRSA in healthy individuals, patients with AD, and subsets of patients with AD. In addition, a clinical trial is in development to evaluate the potential of vitamin D in preventing colonization and infection by these bacteria.
- A clinical trial in adults with mild, moderate, or severe AD to evaluate the immune response in the skin to a yellow fever vaccine given by injection into the skin or by skin scarification (the process of applying a vaccine through multiple superficial scratches). This trial should provide insight into the skin immune responses in individuals with AD and how the vaccinia virus causes EV after smallpox vaccination.
- Clinical trials to evaluate the immune responses to intramuscular administration of the seasonal flu vaccine in healthy people and in patients with AD and ADEH compared to vaccines given into the outer layers of the skin (intradermal).
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