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All About the Itch

What You Should Know about Atopic Dermatitis

by Gil Yosipovitch, MD, and Shawn Kwatra, MD

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Atopic dermatitis, also known as eczema, is a chronic skin disorder affecting hundreds of millions of people around the world. It has been estimated that 10 percent of the population will be affected by atopic dermatitis at some point in their lives. Atopic dermatitis often follows a waxing and waning course, filled with periods of disease flares and periods of remission. While atopic dermatitis may persist to adulthood, infants and young children are most frequently affected. The hallmark of atopic dermatitis is the terrible itch it causes.

What Causes Atopic Dermatitis?
Since Researchers do not know the precise cause of atopic dermatitis, but evidence points to an involvement of both heredi­tary and environmental factors. Atopic dermatitis is part of an allergic triad of conditions that also includes asthma and hay fever (seasonal allergies). These conditions are thought to be caused by an inherited predisposition to an overactive immune system. Indeed, substances called cytokines, which are secreted by cells in the immune system, are often more numerous in people who have atopic dermatitis.

Atopic dermatitis features a vicious itch-scratch cycle. The itch causes you to scratch, and scratching worsens the itch.

author

Dr. Gil Yosipovitch
(Photo by Wake Forest University Creative Communications)

Researchers recently found that people with atopic dermatitis have a genetic defect in filaggrin , a protein that plays a significant role in forming the upper layer of the epidermis, also known as the stratum corneum. With­out sufficient filaggrin, the skin barrier is weakened and becomes accessible and sensitive to germs, allergens, and many other foreign substances. Since a weakened skin barrier increases nerve fibers’ exposure to the environment, people who have atopic dermatitis are more likely to be irritated by exposure to soaps, detergents, and even temperature changes. Because the skin is missing some of its natural building blocks, many people who have atopic dermatitis experience the symptoms of dry skin. This is why people who have atopic dermatitis benefit so much from using moisturizers containing ceramides, substances that are vital to the barrier of the skin because of their ability to replenish it.

author

Dr. Shawn Kwatra
(Photo by Scott Faber Photography)

Skin Manifestations
Since Atopic dermatitis causes significant inflammation and severe itch and scratching, which in combination lead to skin redness and crusting, scaling, and often oozing skin lesions. These lesions often affect the skin folds of the arms and back of the knees and below the ears. People from different ethnic groups often have different presentations of atopic dermatitis.

Itch
Since Itch is the primary symptom of people who have atopic dermatitis. Severe and frequent or constant itch leads to many sleepless nights and severely impairs a person’s quality of life. Itch in atopic dermatitis is aggra­vated by proteases, small proteins that are also secreted by Staphylococcus aureus (a bacterium that is found in the respiratory tract and on the skin) and house dust mites, common triggers of atopic dermatitis flares. Scratching is hard to resist and may lead to thickened and darkened areas of skin, bacterial infections, and worsening rashes. Atopic dermatitis features a vicious itch-scratch cycle. The itch causes you to scratch, and scratching worsens the itch. This cycle keeps repeating itself, leading to damage to the skin barrier as well as breaks in the skin that can lead to infections.

Many people who have atopic der­matitis are not aware of how much they are scratching, particularly during the night, which not only disturbs sleep but further increases skin inflammation.

In addition to interrupting restful sleep, itch in atopic dermatitis can be a contributing factor to psychosocial conditions, including depression, anxi­ety, difficulty concentrating, and poor self-esteem. Similarly, stress is known to be an aggravating factor for itch in people who have atopic dermatitis. Building on this association, a study using brain imaging found that itch in people who have atopic dermatitis significantly differs from itch induced in healthy individuals; that is, itch in people who have atopic dermatitis activated areas of the brain involved in emotion and in the memory of nega­tive experiences. This study highlights the role of cognitive and emotional factors in the exacerbation of itch in atopic dermatitis. Factors aggravating itch in people who have atopic dermatitis can be broadly categorized as follows: environmental triggers, allergens, emotional stress, and infections.

Treatment of Itch
Since The treatment of itch is specialized based on the age and circumstances of the person being treated. However, treatment should focus on two fronts: 1) instiuting measures for prevention of atopic dermatitis-associated itch and 2) providing symptomatic relief for itch associated with current skin lesions.

Preventing Itch
Since People who have atopic dermatitis often have a dis­rupted skin barrier. For this reason, it is important to moisturize the skin as soon as possible after bathing, to replenish the skin barrier and prevent water loss and irritation. (Be sure to select a moisturizer that replenishes ceramide and other lipids that are depleted in the outer layers of the skin in people with atopic dermatitis.)

Indeed, a study found that the amount of water loss in the skin is associated with the intensity of itch. Use low pH cleansers, which are effective at reducing itch because their low pH reduces the activation of nerve fibers that are often overly sensitive to enzymes activated by higher pH cleansers. In addition, you and your family should try to keep a diary documenting the cir­cumstances surrounding episodes of severe itch and use the diary to try to identify an association between itch or increased itch and specific factors.

Relieving Symptoms
Since atopic dermatitis features a hyperactive immune response, drugs that can suppress the immune system (either applied directly to the skin or taken orally) are effective in relieving symptoms of itch associated with atopic dermatitis.

 

Dr. Gil Yosipovitch is a professor and chair of the department of Dermatology and director of the Temple Itch Center at Temple University School of Medicine in Philadelphia, PA. Dr. Shawn Kwatra is a resident in the department of Derma­tology at The Johns Hopkins School of Medicine in Baltimore, MD.

Excerpted with permission from Living with Itch: A Patient’s Guide by Gil Yosipovitch, MD, and Shawn Kwatra, ME, copyright © 2013 by The Johns Hopkins University Press. All rights reserved.

This article was originally published in Coping® with Allergies & Asthma magazine, Winter 2013-2014.